你能帮我吗。我是 android 开发和这个网站的新手。我对烦人的手电筒示例有一点问题。我试图添加频闪功能。它工作正常。但是如果我在 StrobeLightConfig Activity （第二个活动）上按下后退按钮，当切换按钮打开并频闪工作时，我会遇到异常并且应用程序崩溃。如果我在切换按钮关闭时按下后退按钮，一切正常并且工作正常。我认为这个问题与线程。
只有当led频闪灯工作时才会出现这个问题。对不起，如果这个问题已经存在。我试图在这个网站上找到关于这个问题的信息。
日志猫：
11-19 20:28:53.381: E/AndroidRuntime(21737): FATAL EXCEPTION: main
11-19 20:28:53.381: E/AndroidRuntime(21737): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.eugene.android/com.eugene.android.FlashLightActivity}: java.lang.RuntimeException: Fail to connect to camera service
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2194)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2229)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.app.ActivityThread.access$600(ActivityThread.java:139)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1261)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.os.Handler.dispatchMessage(Handler.java:99)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.os.Looper.loop(Looper.java:154)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.app.ActivityThread.main(ActivityThread.java:4944)
11-19 20:28:53.381: E/AndroidRuntime(21737): at java.lang.reflect.Method.invokeNative(Native Method)
11-19 20:28:53.381: E/AndroidRuntime(21737): at java.lang.reflect.Method.invoke(Method.java:511)
11-19 20:28:53.381: E/AndroidRuntime(21737): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
11-19 20:28:53.381: E/AndroidRuntime(21737): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
11-19 20:28:53.381: E/AndroidRuntime(21737): at dalvik.system.NativeStart.main(Native Method)
11-19 20:28:53.381: E/AndroidRuntime(21737): Caused by: java.lang.RuntimeException: Fail to connect to camera service
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.hardware.Camera.native_setup(Native Method)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.hardware.Camera.<init>(Camera.java:307)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.hardware.Camera.open(Camera.java:283)
11-19 20:28:53.381: E/AndroidRuntime(21737): at com.eugene.android.FlashLightActivity.onCreate(FlashLightActivity.java:83)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.app.Activity.performCreate(Activity.java:4524)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1071)
11-19 20:28:53.381: E/AndroidRuntime(21737): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2150)
11-19 20:28:53.381: E/AndroidRuntime(21737): ... 11 more
11-19 20:28:53.391: D/(115): [GECameraParameters::getGPUEffect] enter
11-19 20:28:53.391: D/(115): [GECameraParameters::getGPUEffect] leave. no key GPU-effect
11-19 20:28:53.391: D/(115): [GECameraParameters::getGPUEffectParam] leave. no key GE-param0
11-19 20:28:53.391: D/(115): [GECameraParameters::getGPUEffectParam] leave. no key GE-param1
11-19 20:28:53.391: I/GPUPostEffect(115): int mlabs::GPUPostEffect::setParameters(mlabs::GPUPostEffect::GPUTask*): old effect = -1, new effect = -1.
11-19 20:28:53.391: D/GPUPostEffect(115): setParameters: isGEInit == false: no call to ChooseEffect.
11-19 20:28:53.391: E/EmbeddedLogger(367): App crashed! Process: com.eugene.android
11-19 20:28:53.391: E/EmbeddedLogger(367): App crashed! Package: com.eugene.android v1 (1.0)
11-19 20:28:53.391: E/EmbeddedLogger(367): Application Label: AWESOME Flashlight
11-19 20:28:53.401: W/ActivityManager(367): Force finishing activity com.eugene.android/.FlashLightActivity
11-19 20:28:53.401: W/ActivityManager(367): Force finishing activity com.eugene.android/.StrobeLightConfig
手电筒活动：
public class FlashLightActivity extends Activity {
protected static final Parameters params = null;
private boolean isLighOn = false;
protected Camera camera;
protected RelativeLayout relativeLayout;
private android.widget.TextView TextView;
private android.widget.ImageView ImageView;
public void onStart(){
super.onStart();
}
public void onResume(){
super.onResume();
}
public void onPause(){
super.onPause();
}
public void onStop() {
super.onStop();
if (camera != null) {
camera.release();
}
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
TextView = (android.widget.TextView) findViewById(R.id.textView1);
relativeLayout = (RelativeLayout) findViewById(R.id.relativeLayout1);
ImageView= (android.widget.ImageView) findViewById(R.id.imageView1);
Context context = this;
PackageManager pm = context.getPackageManager();
if (!pm.hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
Log.e("err", "Device has no camera!");
return;
}
camera = Camera.open();
final Parameters p = camera.getParameters();
relativeLayout.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View arg0) {
if (isLighOn) {
relativeLayout.setBackgroundResource(R.drawable.light1);
TextView.setText(R.string.light_off_text);
Log.i("info", "torch is turn off!");
p.setFlashMode(Parameters.FLASH_MODE_OFF);
camera.setParameters(p);
camera.stopPreview();
isLighOn = false;
//ledControl("lcd-backlight", 30);
} else {
Log.i("info", "torch is turn on!");
p.setFlashMode(Parameters.FLASH_MODE_TORCH);
TextView.setText(R.string.light_on_text);
camera.setParameters(p);
camera.startPreview();
isLighOn = true;
relativeLayout.setBackgroundResource(R.drawable.light2);
}
}
});
ImageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v)
{
switch (v.getId())
{
case R.id.imageView1:
Intent intent = new Intent(FlashLightActivity.this, StrobeLightConfig.class);
startActivity(intent);
camera.release();
}
}
});
}
}
频闪灯配置活动：
public class StrobeLightConfig extends FlashLightActivity {
StrobeRunner runner;
Thread bw;
Dialog dialog;
public final Handler mHandler = new Handler();
public final Runnable mShowToastRunnable = new Runnable() {
public void run() {
showMessage();
}
};
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
/* dialog = new Dialog(StrobeLightConfig.this);
dialog.setContentView(R.layout.main1);
dialog.setTitle("Write Message");
dialog.setCancelable(true);
inp = (EditText) dialog.findViewById(R.id.morsetext);
Button okB = (Button) dialog.findViewById(R.id.ok);
Button cancelB = (Button) dialog.findViewById(R.id.cancel);*/
super.onCreate(savedInstanceState);
setContentView(R.layout.main1);
camera.release();
final ToggleButton togglebutton = (ToggleButton) findViewById(R.id.ToggleButton01);
runner = StrobeRunner.getInstance();
runner.controller = this;
if(runner.isRunning)
{
}
else
{
try
{
camera = Camera.open();
if(camera==null)
{
togglebutton.setEnabled(false);
TextView t = (TextView)findViewById(R.id.TextView01);
t.setText(R.string.nocamera);
return;
}
camera.release();
}
catch(RuntimeException ex)
{
togglebutton.setEnabled(false);
TextView t = (TextView)findViewById(R.id.TextView01);
t.setText(R.string.nocamera);
Toast.makeText(getApplicationContext(), "Error connecting to camera flash.", Toast.LENGTH_LONG).show();
return;
}
}
togglebutton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
// Perform action on clicks
if (togglebutton.isChecked()) {
bw = new Thread(runner);
bw.start();
} else {
runner.requestStop = true;
}
}
});
final SeekBar skbar = (SeekBar)findViewById(R.id.SeekBar01);
skbar.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
runner.delay=progress;
}
});
final SeekBar skbaroff = (SeekBar)findViewById(R.id.SeekBar02);
skbaroff.setOnSeekBarChangeListener(new OnSeekBarChangeListener() {
public void onStopTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
public void onStartTrackingTouch(SeekBar seekBar) {
// TODO Auto-generated method stub
}
public void onProgressChanged(SeekBar seekBar, int progress,
boolean fromUser) {
runner.delayoff=progress;
}
});
}
public void onPause()
{
super.onPause();
runner.requestStop=true;
camera.release();
}
@Override
public void onStop() {
super.onStop();
runner.requestStop=true;
ToggleButton togglebutton = (ToggleButton) findViewById(R.id.ToggleButton01);
togglebutton.setChecked(false);
}
public void showMessage()
{
String err = runner.errorMessage;
runner.errorMessage="";
if(!err.equals(""))
{
Context context = getApplicationContext();
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, err, duration);
toast.show();
}
ToggleButton togglebutton = (ToggleButton) findViewById(R.id.ToggleButton01);
togglebutton.setChecked(false);
}
public boolean onKeyDown(int keyCode, KeyEvent event) {
// TODO Auto-generated method stub
if(keyCode == KeyEvent.KEYCODE_BACK){
Intent i = new Intent(StrobeLightConfig.this, FlashLightActivity.class);
startActivity(i);
}
return super.onKeyDown(keyCode, event);
}
}
StrobeRunner 活动：
public class StrobeRunner implements Runnable {
protected StrobeRunner()
{
}
public static StrobeRunner getInstance()
{
return ( instance == null ? instance = new StrobeRunner() : instance );
}
private static StrobeRunner instance;
public volatile boolean requestStop = false;
public volatile boolean isRunning = false;
public volatile int delay = 0;
public volatile int delayoff = 500;
public volatile StrobeLightConfig controller;
public volatile String errorMessage = "";
public void run() {
if(isRunning)
return;
requestStop=false;
isRunning = true;
Camera cam = Camera.open();
Camera.Parameters pon = cam.getParameters(), poff = cam.getParameters();
pon.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
poff.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
while(!requestStop)
{
try{
cam.setParameters(pon);
Thread.sleep(delay);
cam.setParameters(poff);
Thread.sleep(delayoff);
}
catch(InterruptedException ex)
{
}
catch(RuntimeException ex)
{
requestStop = true;
errorMessage = "Error setting camera flash status. Your device may be unsupported.";
}
}
cam.release();
isRunning = false;
requestStop=false;
controller.mHandler.post(controller.mShowToastRunnable);
}
}