在textview中显示当前音频幅度

Question

我认为我非常接近实现我需要的东西，但是在尝试将当前幅度整数转换为textview中的字符串时，我遇到了错误。

所以我的目标是：显示摄像机预览（工作），检测声音（可能正常工作）并在textview（textPowerUp）中显示该声音的当前振幅水平。后来我想用一个计数器替换textview，这个计数器会在检测到声音时计数，然后慢慢倒计时，当它不是，但宝贝步骤......

如果我注释掉这一行，那么没有错误：

txtPowerLevel.setText(Integer.toString(currentAmplitude));

但那是我用来将幅度整数转换为字符串并将其插入到我的textview中的行。这一行给出了一个空引用错误。

我甚至试图强制currentAmplitude的值至少为0：

if (mRecorder.getMaxAmplitude() > 0) {
    currentAmplitude = mRecorder.getMaxAmplitude();
} else {
    currentAmplitude = 0;
}

但这似乎没有帮助。我仍然得到一个空引用错误。我甚至尝试将其他值设置为＆＃39; 1＆＃39; incase＆＃39; 0＆＃39;被视为＆＃39; null＆＃39;但也没有运气。

这是整个课程......请告诉我你是否能发现问题！

public class DBZPowerUp extends AppCompatActivity implements TextureView.SurfaceTextureListener {

    MediaRecorder mRecorder = new MediaRecorder();
    private Handler mHandler = new Handler();
    private Camera mCamera;
    private TextureView mTextureView;
    private int currentAmplitude;


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

        // Variables for textureview
        mTextureView = new TextureView(this);
        mTextureView.setSurfaceTextureListener(this);

        // Build the camera preview onto textureview
        setContentView(mTextureView);

        // Run methods to start audio capture
        startAudioCapture();
        getAmplitude();

        // Repeat audio methods constantly
        mHandler.postDelayed(runnable, 100);

        // Input the current amplitude level into the power level textview
        setCurrentAmplitude();
        TextView txtPowerLevel = (TextView) findViewById(R.id.txtPowerLevel);
        txtPowerLevel.setText(Integer.toString(currentAmplitude));

    }

    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
        mCamera = Camera.open();

        try {
            mCamera.setPreviewTexture(surface);
            mCamera.startPreview();
        } catch(IOException e) {
            Log.e("DBZ_", "Camera broke");
        }
        mCamera.setDisplayOrientation(90);
    }

    @Override
    public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
        // Ignored, Camera does all the work for us
    }

    @Override
    public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
        stopAudioCapture();
        mCamera.stopPreview();
        mCamera.release();
        return true;
    }

    @Override
    public void onSurfaceTextureUpdated(SurfaceTexture surface) {
        // Invoked every time there's a new Camera preview frame
    }

    public void startAudioCapture() {
        mRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
        mRecorder.setOutputFormat(MediaRecorder.OutputFormat.THREE_GPP);
        mRecorder.setAudioEncoder(MediaRecorder.OutputFormat.AMR_NB);
        mRecorder.setOutputFile("/dev/null");
        try {
            mRecorder.prepare();

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        try {
            mRecorder.start();
        }
        catch (IllegalStateException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        }

    public void stopAudioCapture() {
        mRecorder.stop();
        mRecorder.release();
    }

    public double getAmplitude() {
        if (mRecorder != null)
            return  mRecorder.getMaxAmplitude();
        else
            return 0;

    }

    private Runnable runnable = new Runnable() {
        @Override
        public void run() {
      /* do what you need to do */
            getAmplitude();
      /* and here comes the "trick" */
            mHandler.postDelayed(this, 100);
        }
    };

    private void setCurrentAmplitude() {
        if (mRecorder.getMaxAmplitude() > 0) {
            currentAmplitude = mRecorder.getMaxAmplitude();
        } else {
            currentAmplitude = 0;
        }
    }
}

非常感谢先进！

利。

答案（感谢Blackbelt）：

我改变了：

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dbzpowerup);

        // Variables for textureview
        mTextureView = new TextureView(this);
        mTextureView.setSurfaceTextureListener(this);

        // Build the camera preview onto textureview
        setContentView(mTextureView);

要：

   protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dbzpowerup);

        // Define the textureview in XML and apply the surface listener for camera preview
        TextureView mTextureView = (TextureView) findViewById(R.id.textureView1);
        mTextureView.setSurfaceTextureListener(this);