我是Android编程的新手。我正在开发一个简单的应用程序:适用于Android的FlashLight。
如果用户按下menubutton或锁定屏幕,我需要应用程序继续在后台运行。在用户按下按钮停止照明之前,灯不应停止。
以下是我的代码:
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;
}
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;
}
params = camera.getParameters();
params.setFlashMode(Parameters.FLASH_MODE_OFF);
camera.setParameters(params);
camera.stopPreview();
isFlashOn = false;
// changing button/switch image
toggleButtonImage();
}
}
/*
* 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);
}
}
/*
* 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();
}
@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;
}
}
}
答案 0 :(得分:1)
你;关闭onPause灯。当屏幕锁定或应用程序最小化时,将调用onPause。如果您不希望发生这种情况,请不要在那里调用它。
答案 1 :(得分:0)
我认为您正在搜索服务:http://developer.android.com/guide/components/services.html
它们与Activity非常相似,但是dot提供了一个用户界面,可以在后台运行。