Android学习笔记-两个Activity之间传递数据

情景描述：在主界面MainActivity中的EditText控件中输入数据，单击Send按钮，将信息传递到第二Activity中，并在TextView控件中展示

1.在MainActivity的布局文件为activity_main.xml中给按钮设置单击触发事件sendMessage()方法

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <EditText android:id="@+id/edit_message"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send" 
        android:onClick="sendMessage"/>

</LinearLayout>

2.在单击事件sendMessage中建立Intent并通过intent.putExtra携带数据
其中DisplayMessageActivity是信息展示Activity，new intent()方法里有两个参数，第一个为context类型，this代表当前activity，它是继承context；第二个参数为要启动的activity类名

package com.foxhu.myfirstapp;

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

public class MainActivity extends Activity {
	  public final static String EXTRA_MESSAGE = "com.foxhu.myfirstapp.MESSAGE";

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

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.activity_main, menu);
		return true;
	}
	
	public void sendMessage(View view){
		Intent intent = new Intent(this,DisplayMessageActivity.class);
		EditText editText = (EditText)findViewById(R.id.edit_message);
		String message = editText.getText().toString();
		intent.putExtra(EXTRA_MESSAGE, message);
		startActivity(intent);
	}
}

3.创建DisplayMessageActivity

public class DisplayMessageActivity extends Activity {

    @SuppressLint("NewApi")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_display_message);

        // Make sure we're running on Honeycomb or higher to use ActionBar APIs
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            // Show the Up button in the action bar.设置向上返回按钮
            getActionBar().setDisplayHomeAsUpEnabled(true);
        }
      // Get the message from the intent
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

      // Create the text view
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

      // Set the text view as the activity layout
        setContentView(textView);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case android.R.id.home:
            NavUtils.navigateUpFromSameTask(this);
            return true;
        }
        return super.onOptionsItemSelected(item);
    }
}

布局文件activity_display_message.xml，采用线性布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal">

    <EditText android:id="@+id/edit_message"
        android:layout_weight="1"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/edit_message" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send" 
        android:onClick="sendMessage"/>

</LinearLayout>

4.AndroidManifest.xml配置清单

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

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="16" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.foxhu.myfirstapp.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.foxhu.myfirstapp.DisplayMessageActivity"
            android:label="@string/title_activity_display_message"
            android:parentActivityName="com.foxhu.myfirstapp.MainActivity" >
            <meta-data
                android:name="android.support.PARENT_ACTIVITY"
                android:value="com.foxhu.myfirstapp.MainActivity" />
        </activity>
    </application>

</manifest>

5.strings.xml文件

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="app_name">MyFirstApp</string>
    <string name="hello_world">Hello world!</string>
    <string name="menu_settings">Settings</string>
    <string name="edit_message">Enter a message</string>
    <string name="button_send">发送</string>
    <string name="title_activity_display_message">My Message</string>
</resources>

参考资料：http://developer.android.com/training/basics/firstapp/starting-activity.html