Question

我做了一个简单的FlashLight应用程序。运行正常，但是有一个错误。启动应用程序后的第一次第一次按下向下按钮时，它不会启动手电筒。当我再次按下按钮时，它将启动手电筒。

帮我解决这个问题。谢谢！

问题：第一次按下按钮时Flashlight无法启动。

private Camera camera;

private ImageButton flashlightButton;

private TextView Status;

private static final int CAMERA_REQUEST = 123;

boolean hasCameraFlash = false;

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

        ActivityCompat.requestPermissions(MainActivity.this,
                new String[]{Manifest.permission.CAMERA},CAMERA_REQUEST);

        Status = findViewById(R.id.Status);
        flashlightButton = findViewById(R.id.flashlight_button);

        flashlightButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (hasCameraFlash){
                    if (Status.getText().toString().contains("ON")){
                        Status.setText("OFF");
                        flashlightOff();
                    } else {
                      Status.setText("ON");
                      flashlightOn();
                    }
                }else{
                    Toast.makeText(MainActivity.this, "No Flash Available on your device",Toast.LENGTH_SHORT).show();
                }
            }
        });
    }

    private void flashlightOn(){
        CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

        try {
            String cameraId = cameraManager.getCameraIdList()[0];
            cameraManager.setTorchMode(cameraId,true);
            flashlightButton.setImageResource(R.drawable.flashlight_on);
        } catch (CameraAccessException e) {
        }
    }

    private void flashlightOff(){
        CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

        try {
            String camerid = cameraManager.getCameraIdList()[0];
            cameraManager.setTorchMode(camerid,false);
            flashlightButton.setImageResource(R.drawable.flashlight_off);
        } catch (CameraAccessException e){

        }
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        switch (requestCode){
            case CAMERA_REQUEST:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED){
                    hasCameraFlash = getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
                }else{
                    Toast.makeText(MainActivity.this, "Permission Denied for the Camera", Toast.LENGTH_SHORT).show();
                }
                break;
        }
    }
    @Override
    protected void onDestroy() {

        super.onDestroy();
        if (camera != null) {
            camera.stopPreview();
            camera.setPreviewCallback(null);

            camera.release();
            camera = null;
        }


    }

}

Answer 1

使用权限

    <uses-permission android:name="android.permission.FLASHLIGHT" />
    <uses-feature
            android:name="android.hardware.camera.flash"
            android:required="false" />  
      <uses-feature
            android:name="android.hardware.camera"
            android:required="false" />

代码：

 Parameters p = mCamera.getParameters();
    Camera mCamera = Camera.open();
            p = mCamera.getParameters();
            p.setFlashMode(Parameters.FLASH_MODE_ON);
            mPreview = new CameraPreview(mContext, mCamera);
            mCamera.startPreview();

Answer 2

在您的代码中未发现错误。也许在您的XML布局文件中，按钮具有如下属性：

android:onClick="onClick"  //delete if such line exists

另一个可能性是按钮具有如下属性：

android:focusableInTouchMode="true" //delete if such line exists

首次点击时手电筒无法启动

2 个答案: