Intent加强

Intent是一种运行时绑定（runtime binding）机制，它能在程序运行的过程中连接两个不同的组件。通过Intent，你的程序可以向Android表达某种请求或者意愿，Android会根据意愿的内容选择适当的组件来请求。在这些组件之间的通讯中，主要是由Intent协助完成的。Intent负责对应用中一次操作的动作、动作涉及数据、附加数据进行描述，Android则根据此Intent的描述，负责找到对应的组件，将 Intent传递给调用的组件，并完成组件的调用。因此，Intent在这里起着一个媒体中介的作用，专门提供组件互相调用的相关信息，实现调用者与被调用者之间的解耦。

在Activity之间传递数据：在我们的实际应用开发中，不同的Activity之间进行切换的时候不可避免的进行数据传递。下面我们来介绍4种最常用的意图传递方式，这4种方式如下：

1、通过Intent传递数据

 　　我们可以通过Intent类中的putExtra方法可以将简单的数据类型和序列化对象保存到Intent对象中，然后在目标的Activity中使用getXxx方法取出对应的数据。

Main.java

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class Main extends Activity {

    private Button button;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);            // 加载布局文件
        button = (Button) this.findViewById(R.id.button);//
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent intent = new Intent();
                // 在意图中传递数据
                intent.putExtra("name", "张三");
                intent.putExtra("age", 23);
                intent.putExtra("address", "北京");

                intent.setClass(Main.this, OtherActivity.class);

                // 启动意图
                startActivity(intent);
            }
        });
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <Button
        android:id="@+id/button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="测试使用Intent传递数据"></Button>

</LinearLayout>

OtherActivity.java

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;

public class OtherActivity extends Activity {

    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.other);
        textView = (TextView) this.findViewById(R.id.msg);

        Intent intent = getIntent();
        int age = intent.getIntExtra("age", 0);
        String name = intent.getStringExtra("name");
        String address = intent.getStringExtra("address");

        textView.setText("age--->>" + age + "\n" + "name-->>" + name + "\n"
                + "address->>" + address);
    }
}

 other.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/msg"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">
    </TextView>

</LinearLayout>

清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.laoluo.test"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.laoluo.test.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.laoluo.test.OtherActivity"
            android:label="@string/app_name" >
        </activity>
    </application>

</manifest>

2、通过静态变量传递数据

　　使用Intent可以很方便在不同的Activity之间传递数据，这个也是官方推荐的方式，但是也有一定的局限性，就是Intent无法传递不能序列化的对象。我们可以使用静态变量来解决这个问题

Main.java 

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class Main extends Activity {
    /** Called when the activity is first created. */
    private Button button;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        button = (Button) this.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                // 声明一个意图
                Intent intent = new Intent();
                intent.setClass(Main.this, OtherActivity.class);
                //在OtherActivity中先声明需要的静态变量，然后将值赋给OtherActivity中的静态变量
                OtherActivity.age = 23;
                OtherActivity.name = "jack";
                startActivity(intent);
            }
        });
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <Button
        android:id="@+id/button"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="使用静态变量传递数据" />
</LinearLayout>

OtherActivity.java  

package com.laoluo.test;

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class OtherActivity extends Activity {

    private TextView textView;
    public static String name;
    public static int age;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.other);

        textView = (TextView)this.findViewById(R.id.msg);

        textView.setText("-name->>"+name+"\n"+"-age-->>"+age);
    }
}

other.xml  

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <TextView
        android:id="@+id/msg"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">
    </TextView>
</LinearLayout>

清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.laoluo.test"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.laoluo.test.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.laoluo.test.OtherActivity"
            android:label="@string/app_name" >
        </activity>
    </application>

</manifest>

3、通过剪切板传递数据

在Activity之间数据传递还可以利用一些技巧，不管是Windows还是Linux操作系统，都会支持一种叫剪切板的技术，也就是某一个程序将一些数据复制到剪切板上，然后其他的任何程序都可以从剪切板中获取数据。

Main.java 

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.text.ClipboardManager;
import android.view.View;
import android.widget.Button;

public class Main extends Activity {

    private Button button;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        button = (Button) this.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                // 从android系统中调用剪切板的服务
                ClipboardManager clipboardManager = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE);

                String name = "jack";
                clipboardManager.setText(name);//将数据设置到剪切板中

                Intent intent = new Intent(Main.this, OtherActivity.class);
                startActivity(intent);
            }
        });
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <Button
        android:text="使用剪切板传递数据"
        android:id="@+id/button"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
    </Button>
</LinearLayout>

OtherActivity.java

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.text.ClipboardManager;
import android.widget.TextView;

public class OtherActivity extends Activity {

    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.other);

        textView = (TextView) this.findViewById(R.id.msg);

        ClipboardManager clipboardManager = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE);

        String msgString = clipboardManager.getText().toString();//取出剪切板中的内容
        textView.setText(msgString);

    }
}

other.xml  

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <TextView
        android:id="@+id/msg"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent">
    </TextView>
</LinearLayout>

清单文件

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.laoluo.test"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.laoluo.test.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.laoluo.test.OtherActivity"
            android:label="@string/app_name" >
        </activity>
    </application>

</manifest>

该方法还可以用于传递一些比较复杂的数据，比如对象（清单文件和布局文件都一样）

MyData.java(将该对象作为数据在两个Activity之间传递)

import java.io.Serializable;

public class MyData implements Serializable {

    //这里最好给该对象设置一个id：private static final long serialVersionUID = 1L;

    private String name;
    private int age;

    public MyData(String name, int age) {
        super();
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "MyData [name=" + name + ", age=" + age + "]";
    }

}

Main.java

import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.text.ClipboardManager;
import android.util.Base64;
import android.view.View;
import android.widget.Button;

public class Main extends Activity {

    private Button button;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        button = (Button) this.findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                MyData myData = new MyData("jack", 23);
                //将对象转换成字符串
                ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
                String base64String = "";
                try {
                    ObjectOutputStream objectOutputStream = new ObjectOutputStream(byteArrayOutputStream);
                    objectOutputStream.writeObject(myData);
                    base64String = Base64.encodeToString(byteArrayOutputStream.toByteArray(), Base64.DEFAULT);
                    objectOutputStream.close();
                } catch (Exception e) {

                }
                ClipboardManager clipboardManager = (ClipboardManager)getSystemService(Context.CLIPBOARD_SERVICE);
                clipboardManager.setText(base64String);
                Intent intent =new Intent(Main.this,OtherActivity.class);
                startActivity(intent);
            }
        });
    }
}

OtherActivity.java

import java.io.ByteArrayInputStream;
import java.io.ObjectInputStream;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.text.ClipboardManager;
import android.util.Base64;
import android.widget.TextView;

public class OtherActivity extends Activity {

    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.other);

        textView = (TextView) this.findViewById(R.id.msg);

        ClipboardManager clipboardManager = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE);

        String msgString = clipboardManager.getText().toString();//取出剪切板中的内容

        byte[] base64_byte = Base64.decode(msgString, Base64.DEFAULT);
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(base64_byte);
        try {
            ObjectInputStream objectInputStream = new ObjectInputStream(byteArrayInputStream);
            MyData myData = (MyData) objectInputStream.readObject();
            textView.setText(myData.toString());
        } catch (Exception e) {

        }

    }
}

4、通过全局变量传递数据

在Activity之间数据传递中还有一种比较实用的方式，就是全局对象，实用J2EE的读者来说都知道Java Web的四个作用域，这四个作用域从小到大分别是Page、Request、Session和Application，其中Application域在应用程序的任何地方都可以使用和访问，除非是Web服务器停止，Android中的全局对象非常类似于Java Web中的Application域，除非是Android应用程序清除内存，否则全局对象将一直可以访问。

Main.java

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;

public class Main extends Activity {
    private Button button;
    private MyApp myApp;
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        button = (Button)this.findViewById(R.id.button);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myApp = (MyApp)getApplication();
                myApp.setName("jack");//修改之后的名称

                Intent intent = new Intent(Main.this,OtherActivity.class);
                startActivity(intent);
            }
        });
    }
}

main.xml（同上一个实例一样）

OtherActivity.java  

import android.app.Activity;
import android.os.Bundle;
import android.widget.TextView;

public class OtherActivity extends Activity {

    private MyApp myApp;
    private TextView textView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.other);

        textView = (TextView)this.findViewById(R.id.msg);

        myApp = (MyApp)getApplication();

        textView.setText("-appname-->>"+myApp.getName());
    }
}

MyApp.java

import android.app.Application;

public class MyApp extends Application {

    public String name;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public void onCreate() {
        super.onCreate();
        setName("张三");
    }
}

other.xml  （同上一个实例一样）

清单文件 （该方法清单文件上的配置有点区别，除了注册一个Activity之外，还要在application标签内标注全局应用， android:name=".MyApp"这个app的名称要跟全局应用的名称一致）

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.laoluo.test"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="18" />

    <application
        android:name=".MyApp"
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.laoluo.test.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name="com.laoluo.test.OtherActivity"
            android:label="@string/app_name" >
        </activity>
    </application>

</manifest>

从Activity中返回数据

在实际的应用中，我们不仅仅要向Activity传递数据，而且要从Activity中返回数据，虽然返回数据和传递数据类似，也可以采用前面4种方法，但是一般建议采用Intent对象的方式来返回数据，使用这种方式返回数据，需要使用startActivityForResult方法来显示Activity。

Main.java

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;

public class Main extends Activity {

    private Button button;
    private final static int REQUESTCODE = 1;    //返回的结果码
    private EditText one,two,result;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        button = (Button) this.findViewById(R.id.button);
        one = (EditText)this.findViewById(R.id.one);
        two = (EditText)this.findViewById(R.id.two);
        result = (EditText)this.findViewById(R.id.result);

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                int a = Integer.parseInt(one.getText().toString());
                int b = Integer.parseInt(two.getText().toString());

                Intent intent = new Intent(Main.this, OtherActivity.class);
                intent.putExtra("a", a);
                intent.putExtra("b", b);

                //启动Intent
                startActivityForResult(intent, REQUESTCODE);//启动意图的另一种方法，这种方法可以返回结果，
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if(resultCode==2){
            if(requestCode==REQUESTCODE){
                int three = data.getIntExtra("three", 0);
                result.setText(String.valueOf(three));
            }
        }
    }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="fill_parent"
    android:layout_height="fill_parent">

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
            <EditText
                android:id="@+id/one"
                android:layout_width="80dp"
                android:layout_height="wrap_content">
            </EditText>

            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text=" + ">
            </TextView>
            <EditText
                android:id="@+id/two"
                android:layout_width="80dp"
                android:layout_height="wrap_content">
            </EditText>
            <TextView
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:text=" = ">
            </TextView>
            <EditText
                android:id="@+id/result"
                android:layout_width="80dp"
                android:layout_height="wrap_content">
            </EditText>
    </LinearLayout>
    <Button
        android:id="@+id/button"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="计算结果">
    </Button>

</LinearLayout>

OtherActivity.java

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class OtherActivity extends Activity {

    private Button button;
    private TextView textView;
    private EditText editText;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.other);

        button = (Button)this.findViewById(R.id.button2);
        textView = (TextView)this.findViewById(R.id.msg);
        editText = (EditText)this.findViewById(R.id.three);

        Intent intent = getIntent();

        int a = intent.getIntExtra("a", 0);
        int b = intent.getIntExtra("b", 0);

        textView.setText(a+" + "+b+" = "+" ? ");

        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

               Intent intent = new Intent();
               int three = Integer.parseInt(editText.getText().toString());

               intent.putExtra("three", three);

               //通过Intent对象返回结果，setResult方法，
               setResult(2, intent);
               finish();//结束当前的Activity的生命周期。
            }
        });
    }
}

other.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical">

    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">
            <TextView
                android:id="@+id/msg"
                android:layout_width="match_parent"
                android:layout_height="wrap_content">
            </TextView>

            <EditText
                android:id="@+id/three"
                android:layout_width="match_parent"
                android:layout_height="wrap_content">
            </EditText>
    </LinearLayout>
    <Button
        android:id="@+id/button2"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="返回结果">
    </Button>

</LinearLayout>