android 开启闪光灯小应用

该程序需要在AndroidManifest.xml添加权限,属性 android:screenOrientation=”portrait”  

android.permission.CAMERA   
android.hardware.camera   

代码:(待解决问题:开关按钮失效)

package com.androidhive.flashlight; import android.app.Activity;import android.app.AlertDialog;import android.content.DialogInterface;import android.content.pm.PackageManager;import android.hardware.Camera;import android.hardware.Camera.Parameters;import android.media.MediaPlayer;import android.media.MediaPlayer.OnCompletionListener;import android.os.Bundle;import android.util.Log;import android.view.View;import android.widget.ImageButton; public class MainActivity extends Activity {     ImageButton btnSwitch;     private Camera camera;    private boolean isFlashOn;    private boolean hasFlash;    Parameters params;    MediaPlayer mp;     @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);         // flash switch button        btnSwitch = (ImageButton) findViewById(R.id.btnSwitch);              // First check if device is supporting flashlight or not                hasFlash = getApplicationContext().getPackageManager()                .hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);         if (!hasFlash) {            // device doesn't support flash            // Show alert message and close the application            AlertDialog alert = new AlertDialog.Builder(MainActivity.this)                    .create();            alert.setTitle("Error");            alert.setMessage("Sorry, your device doesn't support flash light!");            alert.setButton("OK", new DialogInterface.OnClickListener() {                public void onClick(DialogInterface dialog, int which) {                    // closing the application                    finish();                }            });            alert.show();            return;        }         // get the camera        getCamera();                 // displaying button image        toggleButtonImage();                          // Switch button click event to toggle flash on/off        btnSwitch.setOnClickListener(new View.OnClickListener() {             @Override            public void onClick(View v) {                if (isFlashOn) {                    // turn off flash                    turnOffFlash();                } else {                    // turn on flash                    turnOnFlash();                }            }        });    }          // Get the camera    private void getCamera() {        if (camera == null) {            try {                camera = Camera.open();                params = camera.getParameters();            } catch (RuntimeException e) {                Log.e("Camera Error. Failed to Open. Error: ", e.getMessage());            }        }    }           // Turning On flash    private void turnOnFlash() {        if (!isFlashOn) {            if (camera == null || params == null) {                return;            }            // play sound            playSound();                         params = camera.getParameters();            params.setFlashMode(Parameters.FLASH_MODE_TORCH);            camera.setParameters(params);            camera.startPreview();            isFlashOn = true;                         // changing button/switch image            toggleButtonImage();        }     }      // Turning Off flash    private void turnOffFlash() {        if (isFlashOn) {            if (camera == null || params == null) {                return;            }            // play sound            playSound();                         params = camera.getParameters();            params.setFlashMode(Parameters.FLASH_MODE_OFF);            camera.setParameters(params);            camera.stopPreview();            isFlashOn = false;                         // changing button/switch image            toggleButtonImage();        }    }           // Playing sound     // will play button toggle sound on flash on / off    private void playSound(){        if(isFlashOn){            mp = MediaPlayer.create(MainActivity.this, R.raw.light_switch_off);        }else{            mp = MediaPlayer.create(MainActivity.this, R.raw.light_switch_on);        }        mp.setOnCompletionListener(new OnCompletionListener() {             @Override            public void onCompletion(MediaPlayer mp) {                // TODO Auto-generated method stub                mp.release();            }        });         mp.start();    }         /*     * Toggle switch button images     * changing image states to on / off     * */    private void toggleButtonImage(){        if(isFlashOn){            btnSwitch.setImageResource(R.drawable.btn_switch_on);        }else{            btnSwitch.setImageResource(R.drawable.btn_switch_off);        }    }     @Override    protected void onDestroy() {        super.onDestroy();    }     @Override    protected void onPause() {        super.onPause();                 // on pause turn off the flash        turnOffFlash();    }     @Override    protected void onRestart() {        super.onRestart();    }     @Override    protected void onResume() {        super.onResume();                 // on resume turn on the flash        if(hasFlash)            turnOnFlash();    }     @Override    protected void onStart() {        super.onStart();                 // on starting the app get the camera params        getCamera();    }     @Override    protected void onStop() {        super.onStop();                 // on stop release the camera        if (camera != null) {            camera.release();            camera = null;        }    } }