最近在学习Android的开发，写了个手电筒的案例，分享一下！

//Activity.xml
package com.fq.flashlight;import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.TextView;public class LightActivity extends Activity {Button button           = null;        //创建Button类型的变量TextView textView        = null;        //创建TextView类型的变量Camera camera          = null;        //创建Camera类型的变量Parameters params        = null;        //创建Parameters类型的变量Boolean flag             = true;        //创建Boolean类型的变量，用于做是否开启的判断@Overrideprotected void onCreate(Bundle savedInstanceState){super.onCreate(savedInstanceState);setContentView(R.layout.activity_light);button = (Button)findViewById(R.id.button);      //获取Button对象textView = (TextView) findViewById(R.id.textView); //获取TextView对象button.setOnClickListener(new OnClickListener() {     //点击事件@Overridepublic void onClick(View v) {if(flag){camera = Camera.open();    //获取摄像头params = camera.getParameters();params.setFlashMode(Parameters.FLASH_MODE_TORCH);camera.setParameters(params);camera.startPreview();textView.setText(R.string.alert_on);button.setText(R.string.button_off);flag = false;}else{params.setFlashMode(Parameters.FLASH_MODE_OFF);camera.setParameters(params);camera.stopPreview();camera.release();textView.setText(R.string.alert_off);button.setText(R.string.button_on);flag = true;}}});}public void onBackPressed(){//super.onBackPressed();System.out.println("sdsfs");new AlertDialog.Builder(this).setTitle("确定退出吗？").setIcon(R.drawable.ic_launcher).setPositiveButton("OK", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface arg0, int arg1) {// TODO Auto-generated method stubLightActivity.this.finish();System.exit(0);}}).setNegativeButton("Cancel", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface arg0, int arg1) {// TODO Auto-generated method stub}}).show();}
}

<!--strings.xml-->
<?xml version="1.0" encoding="utf-8"?>
<resources><string name="app_name">BlueOcean手电筒</string><string name="hello_world">Hello world!</string><string name="action_settings">Settings</string><string name="alert_on">手电筒当前状态：开启</string><string name="alert_off">手电筒当前状态：关闭</string><string name="button_on">开启手电</string><string name="button_off">关闭手电</string><string name="author">Author：BlueOcean</string>
</resources>

<!--layout.xml-->
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"android:layout_width="match_parent"android:layout_height="match_parent" ><TextViewandroid:id="@+id/textView"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignParentTop="true"android:layout_centerHorizontal="true"android:layout_marginTop="34dp"android:text="@string/alert_off"android:textSize="22sp" /><Buttonandroid:id="@+id/button"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_below="@+id/textView"android:layout_centerHorizontal="true"android:layout_marginTop="26dp"android:text="@string/button_on" /><TextViewandroid:id="@+id/textView2"android:layout_width="wrap_content"android:layout_height="wrap_content"android:layout_alignRight="@+id/textView"android:layout_centerVertical="true"android:text="@string/author"android:textAppearance="?android:attr/textAppearanceSmall" />
</RelativeLayout>

<!-- manifest.xml-->
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.fq.flashlight"android:versionCode="1"android:versionName="1.0" ><uses-sdkandroid:minSdkVersion="8"android:targetSdkVersion="21" /><uses-permission android:name="android.permission.CAMERA"/><uses-permission android:name="android.permission.FLASHLIGHT"/><applicationandroid:allowBackup="true"android:icon="@drawable/ic_launcher"android:label="@string/app_name"android:theme="@style/AppTheme" ><activityandroid:name=".MainActivity"android:label="@string/app_name" ></activity><activityandroid:name=".LightActivity"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>