调用另一个Activity

参考自Google官方文档Traning/Getting Started/Building a simple user interface, Startinganother activity，http://developer.android.com/training/basics/firstapp/building-ui.html

1、创建主Activity

使用Eclipse新建项目MyFirstApp,UI布局如下：

<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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:orientation="horizontal"
tools:context=".MainActivity">

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

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/click"
android:onClick="sendMessage"/>

</LinearLayout>

注意通过权重来分配尺寸的方式
组件1：

android:layout_width="0dp"
android:layout_weight="1"

组件2：

android:layout_width="wrap_content"

2、在主类中指定onclick所对应的sendMessage方法

package com.lujinhong.androidtraningmyfirstapp;

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.lujinhong.myfirstapp.MESSAGE";

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

@Override
public boolean onCreateOptionsMenu(Menu menu){
// Inflate themenu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

public void sendMessage(View v){

EditText et_message=(EditText)this.findViewById(R.id.et_message);
String message= et_message.getText().toString().trim();

Intent intent= new Intent(this,DisplayMessageActivity.class);
intent.putExtra(EXTRA_MESSAGE, message);

this.startActivity(intent);

}

}

（1）关于intent
An Intent isan object that provides runtime binding between separate components (such astwo activities). TheIntent representsan
app’s "intent to do something." You can use intents for a widevariety of tasks,
but most often they’re used to startanother activity.

（2）调用另一个activity的步骤：

l 首先取得editText中的文字

EditText et_message = (EditText) this.findViewById(R.id.et_message);
String message = et_message.getText().toString().trim();

l 然后创建一下intent，并把文字作为K-V形式保存到intent中

Intent intent= new Intent(this,DisplayMessageActivity.class);
intent.putExtra(EXTRA_MESSAGE, message);

创建intent时，通过一个类名，指定调用哪个类文件。

l 最后启动一个新的activity.

this.startActivity(intent);

3、显示另一个Activity

package com.lujinhong.androidtraningmyfirstapp;

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

public class DisplayMessageActivityextends Activity{

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

// Get the messagefrom the intent
Intent intent= getIntent();
String message= intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

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

// Set the textview as the activity layout
setContentView(textView);

}

@Override
public boolean onCreateOptionsMenu(Menu menu){
// Inflate themenu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.display_message, menu);
return true;
}

}