Android笔记(3)---Activity和Intent

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Android

认识Activity
Activity是应用程序的一个组件
详解Android的Activity组件
创建Activity
1. 一个Activity就是一个类，并且这个类要继承Activity
2. 需要覆写onCreate方法
3. 第一个Activity都需要在AndroidManifest.xml文件中进行配置
4. 为Activity添加必要控件
向Activity添加一个组件
res/layout/main.xml 布局文件
在一个Activity当中启动另外一个Activity的方法
参照第二个例子：Activity002
使用Intent在Activity之间传递数据的基本方法
参照第二个例子：Activity002
为控件添加监听器
注：使用内部类的好处：可以调用外部类的成员变量和成员方法

例中所贴代码为以下几部分代码：

java代码

res/layout/activity_xxx.xml

res/values/strings.xml

AndroidManifest.xml

-----------------------------------------------------------------------------------

第一个例子：Activity001

MainActivity.java

package com.example.activity001;

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

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        TextView myTextView = (TextView)findViewById(R.id.myTextView);
    
        Button myButton = (Button) findViewById(R.id.myButton);
        
        myTextView.setText("我的第一个TextView");
        myButton.setText("我的第一个Button");
    }


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

res/laout/activity_main.xml

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

    <TextView
        android:id="@+id/myTextView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <Button
        android:id="@+id/myButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

res/values/strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Activity001</string>
    <string name="action_settings">Settings</string>
    <string name="hello_world">Hello world!</string>

</resources>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.activity001"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="9"
        android:targetSdkVersion="9" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.activity001.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>
    </application>

</manifest>

运行效果：

-------------------------------------------------------------------------------------------------------------

第二个例子：Activity002

MainActivity.java

package com.example.activity002;

import android.app.Activity;
import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends Activity {

    // 用于跳转到另一个Activity
    private Button myButton = null;

    // 用于发短信
    private Button sendButton = null;

    private TextView myTextView = null;

    private static int count = 0;

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

        myTextView = (TextView) findViewById(R.id.myTextView);
        myTextView.setText("这是第一个Activity\tcount: " + (count++));

        myButton = (Button) findViewById(R.id.myButton);
        myButton.setText("跳转到第二个Activity");
        myButton.setOnClickListener(new MyButtonListener());

        sendButton = (Button) findViewById(R.id.sendButton);
        sendButton.setText("跳转到发送短信Activity");
        sendButton.setOnClickListener(new SendButtonListener());


    }

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


    class MyButtonListener implements OnClickListener {

        @Override
        public void onClick(View v) {
            Intent intent = new Intent();
            intent.setClass(MainActivity.this, SecondActivity.class);

            // 两个Activity之间传递参数
            intent.putExtra("activity_param_001", "参数值来自Activity");

            MainActivity.this.startActivity(intent);
        }

    }

    class SendButtonListener implements OnClickListener {

        @Override
        public void onClick(View v) {
            // 实现了一次转变到发送短信的界面。
            // Uri uri = Uri.parse("smsto://730371432");
            Uri uri = Uri.parse("smsto:18352507379");
            Intent intent = new Intent(Intent.ACTION_SENDTO, uri);
            // 这个程序是存放的是键值对
            intent.putExtra("sms_body", "the SMS text");
            // 这个程序也可以写作:startActivity(intent);表示的启动
            MainActivity.this.startActivity(intent);
        }

    }


}

SecondActivity.java

package com.example.activity002;

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

public class SecondActivity extends Activity {

    // 返回到第一个Activity
    private Button myButton = null;

    private TextView myTextView = null;

    private TextView showTextView = null;

    private static int count = 0;

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

        myTextView = (TextView) findViewById(R.id.my2TextView);
        myTextView.setText("这是第二个Activity\tcount: " + (count++));


        myButton = (Button) findViewById(R.id.my2Button);
        myButton.setText("跳转到第一个Activity");
        myButton.setOnClickListener(new My2ButtonListener());


        Intent intent = getIntent();
        String paramValue = intent.getStringExtra("activity_param_001");
        showTextView = (TextView) findViewById(R.id.showTextView);
        showTextView.setText(paramValue);
    }


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


    class My2ButtonListener implements OnClickListener {

        @Override
        public void onClick(View v) {
            Intent intent = new Intent();
            intent.setClass(SecondActivity.this, MainActivity.class);

            SecondActivity.this.startActivity(intent);
        }

    }
}

布局文件

res/layout/activity_main.xml

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

    <TextView
        android:id="@+id/myTextView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/activity_001" />

    <Button
        android:id="@+id/myButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/sendButton"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

res/layout/activity_second.xml

<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="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".SecondActivity" >

    <TextView
        android:id="@+id/my2TextView"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="@string/activity_002" />

    <Button
        android:id="@+id/my2Button"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

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

</LinearLayout>

res/values/strings.xml

<?xml version="1.0" encoding="utf-8"?>
<resources>

    <string name="app_name">Activity002</string>
    <string name="action_settings">Settings</string>
    <string name="hello_world">Hello world!</string>
    <string name="activity_001">第一个Activity</string>
    <string name="activity_002">第二个Activity</string>

</resources>

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.activity002"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="9"
        android:targetSdkVersion="9" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".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=".SecondActivity"
            android:label="@string/app_name" >
        </activity>
    </application>

</manifest>

运行效果: