在文本视图中显示当前音频幅度

Question

我认为我已经非常接近实现我需要的目标了，但是在尝试将我当前的振幅整数转换为文本视图中的字符串时出现错误。

所以我的目标是：显示相机预览（有效）、检测声音（可能有效）并在文本视图 (textPowerUp) 中显示该声音的当前振幅级别。稍后我想用一个计数器替换 textview，该计数器在检测到声音时计数，在没有检测到声音时慢慢倒数，但是婴儿步骤...

所以如果我注释掉以下行就不会出错：

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

但这就是我 - 试图 - 用来将振幅整数转换为字符串并将其插入到我的文本视图中的行。而这一行给出了空引用错误。

我什至试图强制 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。我仍然收到空引用错误。我什至尝试将 else 的值设置为 '1' 以防 '0' 被视为 'null' 但也没有运气。

这是完整的 class...如果您能发现问题，请告诉我！

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！

李.

回答（感谢 Blackbelt）：

我改了：

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);

收件人：

   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);

Answer 1

你的NPE问题是由于

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

这样你就覆盖了他之前对 setContentView 的调用，它可能包含你的 TextView。您可以将 TextureView 添加到 dbzpowerup.xml 并使用 findViewById 获取对它的引用

在文本视图中显示当前音频幅度

Show current audio amplitude in textview

android

android-mediarecorder