1、activity_main.xml 两个按钮，一个open一个close

<RelativeLayout 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"
tools:context=".MainActivity" >

<TextView
android:id="@+id/textView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="@string/hello_world" />

<Button
android:id="@+id/button_open"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/textView1"
android:layout_below="@+id/textView1"
android:layout_marginTop="38dp"
android:text="open" />

<Button
android:id="@+id/button_close"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/button_open"
android:layout_below="@+id/button_open"
android:layout_marginTop="50dp"
android:text="close" />

</RelativeLayout>

2、MainActivity 核心代码

package com.qiantu.flashlight;

import android.app.Activity;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {
private Camera camera;
private Button openBtn;
private Button closeBtn;

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

openBtn = (Button) findViewById(R.id.button_open);
openBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (null != camera) {
Parameters parameters = camera.getParameters();
parameters.setFlashMode(Parameters.FLASH_MODE_TORCH);
camera.setParameters(parameters);
}
}
});

closeBtn = (Button) findViewById(R.id.button_close);
closeBtn.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (null != camera) {
Parameters parameters = camera.getParameters();
parameters.setFlashMode(Parameters.FLASH_MODE_OFF);
camera.setParameters(parameters);
}
}
});
}

@Override
protected void onStart() {
super.onStart();
camera = Camera.open();
}

@Override
protected void onDestroy() {
super.onDestroy();
if (null != camera) {
camera.release();
}
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}

3、AndroidManifest.xml 加入摄像头和闪关灯的权限

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

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

<!-- 添加的部分 -->
<uses-feature android:name="android.hardware.camera" />
<uses-feature android:name="android.hardware.autofocus" />
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.FLASHLIGHT" />
<uses-permission android:name="android.permission.DISABLE_KEYGUARD" />
<!-- end -->

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