java - Nexus 5 上的 Android 手电筒

Question

我正在尝试开发一个应用程序，用于在点击切换按钮时打开手电筒。我尝试了我在网上找到的所有方法，但在我的 nexus 5 中没有成功。唯一可用的应用程序是 cyanogenmod torch，但即使我采用该代码并将其写入我的应用程序，它也会创建一个通知，如果单击它会打开cyanogenmod torch 应用程序，而不是我的!这是个问题!!有没有可能有一个简单的代码也适用于 nexus 5？

public void turnOffFlashLight() {
    try {
        if (getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH)) {
            cam.stopPreview();
            cam.release();
            cam = null;
        }
    } catch (Exception e) {
        e.printStackTrace();
        Toast.makeText(getBaseContext(), "Exception throws in turning off flashlight.", Toast.LENGTH_SHORT).show();
    }
}

public void turnOnFlashLight() {
    try {
        if (getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH)) {
            cam = Camera.open();
            cam.setPreviewTexture(new SurfaceTexture(0));
            Parameters p = cam.getParameters();
            p.setFlashMode(Parameters.FLASH_MODE_TORCH);

            cam.setParameters(p);
            cam.startPreview();
        }
    } catch (Exception e) {
        e.printStackTrace();
        Toast.makeText(getBaseContext(), "Exception throws in turning on flashlight.", Toast.LENGTH_SHORT).show();
    }
}

编辑:logcat

04-09 21:52:21.967: E/AndroidRuntime(5346): FATAL EXCEPTION: main
04-09 21:52:21.967: E/AndroidRuntime(5346): Process: com.lob.twixlight, PID: 5346
04-09 21:52:21.967: E/AndroidRuntime(5346): android.util.SuperNotCalledException: Activity {com.lob.twixlight/com.lob.twixlight.MainActivityTwixLight} did not call through to super.onStart()
04-09 21:52:21.967: E/AndroidRuntime(5346):     at android.app.Activity.performStart(Activity.java:5243)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2178)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at android.app.ActivityThread.access$800(ActivityThread.java:145)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at android.os.Handler.dispatchMessage(Handler.java:102)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at android.os.Looper.loop(Looper.java:136)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at android.app.ActivityThread.main(ActivityThread.java:5081)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at java.lang.reflect.Method.invokeNative(Native Method)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at java.lang.reflect.Method.invoke(Method.java:515)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
04-09 21:52:21.967: E/AndroidRuntime(5346):     at dalvik.system.NativeStart.main(Native Method)

整个主要 Activity

public class MainActivity extends Activity implements Callback  { 


    private ImageView imageView3;
    private ImageButton mButtonOn;
    private Camera cam;
    private SurfaceHolder mHolder ;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        this.requestWindowFeature(Window.FEATURE_NO_TITLE);
        new AlertDialog.Builder(this);
        setContentView(R.layout.activity_main);
        mButtonOn = (ImageButton) findViewById(R.id.my_button);
        imageView3 = (ImageView) findViewById(R.id.imageView3);


        SurfaceView preview = (SurfaceView)findViewById(R.id.PREVIEW);
        mHolder = preview.getHolder();
        mHolder.addCallback(this);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    public void info(View v) {
        Intent intent = new Intent(this, FullscreenActivity.class);
        startActivity(intent);
        overridePendingTransition(R.anim.in, R.anim.out);
    }

    protected void onStart() {
        super.onStart ();
        SurfaceView preview = (SurfaceView)findViewById(R.id.PREVIEW);
        mHolder = preview.getHolder();
        mHolder.addCallback(this);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        mHolder = holder;

        try {
            Log.i("SurfaceHolder", "setting preview");
            cam.setPreviewDisplay(mHolder);  
        } catch (IOException e){
            e.printStackTrace();
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub
        cam.stopPreview();

        mHolder = null;
    }


}

Answer 1

好的，首先，确保您已经将表面 View 添加到您的 xml 布局中，在您的按钮之上:

<SurfaceView
    android:id="@+id/PREVIEW"
    android:layout_width="1dp"
    android:layout_height="1dp"/>

//image button comes below

<ImageButton
    android:id="@+id/my_button" /> 

现在，在您的 java 类中，实现 SurfaceHolder.Callback 接口(interface)，例如:

public class MyFlashlight extends Activity implements Callback

这将自动生成三个回调方法:

surfaceChanged();
surfaceCreated();
surfaceDestroyed();

暂时保持原样。在你的 onStart();方法，添加以下内容:

SurfaceView preview = (SurfaceView)findViewById(R.id.PREVIEW);
SurfaceHolder mHolder = preview.getHolder();
mHolder.addCallback(this);

不要将它添加到 onCreate();因为它(onCreate()；)只被调用一次，如果要重新启动 Activity ，它将导致问题。

在你的 turnOnFlash();方法，照常做:

//get parameters
//set parameters
//set flashmode
//start preview

在你的 surfaceCreated();方法，添加这个:

mHolder = holder;
        try {
            Log.i("SurfaceHolder", "setting preview");
            camera.setPreviewDisplay(mHolder);  
        } catch (IOException e){
            e.printStackTrace();
        }

在你的 surfaceDestroyed();方法，停止预览:

camera.stopPreview();
mHolder = null;

离开surfaceChanged();空

就是这样!!!!试试吧!

这是一个完整的工作示例:

import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MyFlashLight extends Activity implements Callback{

//flag to detect flash is on or off
private boolean isLighOn = false;

private Camera camera;

private Button button;

    @Override
protected void onStart() {
    super.onStart();

         SurfaceView preview = (SurfaceView)findViewById(R.id.PREVIEW);
                SurfaceHolder mHolder = preview.getHolder();
                mHolder.addCallback(this);
    }
}

@Override
protected void onStop() {
    super.onStop();

    if (camera != null) {
        camera.release();
    }
}

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    button = (Button) findViewById(R.id.buttonFlashlight);

    Context context = this;
    PackageManager pm = context.getPackageManager();

    // if device support camera?
    if (!pm.hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
        Log.e("err", "Device has no camera!");
        return;
    }

    camera = Camera.open();
    final Parameters p = camera.getParameters();

    button.setOnClickListener(new OnClickListener() {

        @Override
        public void onClick(View arg0) {

            if (isLighOn) {
                                turnOffFlash();
            } else {
                                turnOnFlash();
                          }
                     }
    });


            private void turnOnFlash(){
            Log.i("info", "torch is turn on!");

                p.setFlashMode(Parameters.FLASH_MODE_TORCH);

                camera.setParameters(p);
                camera.startPreview();
                isLighOn = true;

            }
            private void turnOffFlash(){
            Log.i("info", "torch is turn off!");

                p.setFlashMode(Parameters.FLASH_MODE_OFF);
                camera.setParameters(p);
                camera.stopPreview();
                isLighOn = false;
    @Override
    public void surfaceChanged(SurfaceHolder holder,int format,int width,int height){

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder){
        mHolder = holder;
        try {
            Log.i("SurfaceHolder", "setting preview");
            camera.setPreviewDisplay(mHolder);  
        } catch (IOException e){
            e.printStackTrace();
        }
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder){
        Log.i("SurfaceHolder", "stopping preview");
        camera.stopPreview();
        mHolder = null;
    }

}