Question

I want to create the wave forms of audio file in android. Can anyone provide me an example source code?

Answer 1

Create class and extend View. Then create Listener interface for your class.

public class WaveformCls extends View {
    public interface WaveformListener {
        public void waveformTouchStart(float x);
        public void waveformTouchMove(float x);
        public void waveformTouchEnd();
        public void waveformFling(float x);
        public void waveformDraw();
    };  

Create Paint object as per your requirement.
Create one method which is initialized all Paint object.

public WaveformView(Context context, AttributeSet attrs) {
        super(context, attrs);

        // We don't want keys, the markers get these
        setFocusable(false);

        mGridPaint = new Paint();
        mGridPaint.setAntiAlias(false);
        mGridPaint.setColor(
            getResources().getColor(R.drawable.grid_line));
        mSelectedLinePaint = new Paint();
        mSelectedLinePaint.setAntiAlias(false);
        mSelectedLinePaint.setColor(
            getResources().getColor(R.drawable.waveform_selected));
        mUnselectedLinePaint = new Paint();
        mUnselectedLinePaint.setAntiAlias(false);
        mUnselectedLinePaint.setColor(
            getResources().getColor(R.drawable.waveform_unselected));
        mUnselectedBkgndLinePaint = new Paint();
        mUnselectedBkgndLinePaint.setAntiAlias(false);
        mUnselectedBkgndLinePaint.setColor(
            getResources().getColor(
                R.drawable.waveform_unselected_bkgnd_overlay));
        mBorderLinePaint = new Paint();
        mBorderLinePaint.setAntiAlias(true);
        mBorderLinePaint.setStrokeWidth(1.5f);
        mBorderLinePaint.setPathEffect(
            new DashPathEffect(new float[] { 3.0f, 2.0f }, 0.0f));
        mBorderLinePaint.setColor(
            getResources().getColor(R.drawable.selection_border));
        mPlaybackLinePaint = new Paint();
        mPlaybackLinePaint.setAntiAlias(false);
        mPlaybackLinePaint.setColor(
            getResources().getColor(R.drawable.playback_indicator));
        mTimecodePaint = new Paint();
        mTimecodePaint.setTextSize(12);
        mTimecodePaint.setAntiAlias(true);
        mTimecodePaint.setColor(
            getResources().getColor(R.drawable.timecode));
        mTimecodePaint.setShadowLayer(
            2, 1, 1,
            getResources().getColor(R.drawable.timecode_shadow));

    mGestureDetector = new GestureDetector(
            context,
        new GestureDetector.SimpleOnGestureListener() {
            public boolean onFling(
                    MotionEvent e1, MotionEvent e2, float vx, float vy) {
            mListener.waveformFling(vx);
            return true;
            }
        });

        mSoundFile = null;
        mLenByZoomLevel = null;
        mValuesByZoomLevel = null;
        mHeightsAtThisZoomLevel = null;
        mOffset = 0;
        mPlaybackPos = -1;
        mSelectionStart = 0;
        mSelectionEnd = 0;
        mDensity = 1.0f;
        mInitialized = false;
    }

You need to override onTouchEvent

@Override
    public boolean onTouchEvent(MotionEvent event) {
    if (mGestureDetector.onTouchEvent(event)) {
        return true;
    }

        switch(event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            mListener.waveformTouchStart(event.getX());
            break;
        case MotionEvent.ACTION_MOVE:
            mListener.waveformTouchMove(event.getX());
            break;
        case MotionEvent.ACTION_UP:
            mListener.waveformTouchEnd();
            break;
        }
        return true;
    }

public void setSoundFile(CheapSoundFile soundFile) {
    mSoundFile = soundFile;
    mSampleRate = mSoundFile.getSampleRate();
    mSamplesPerFrame = mSoundFile.getSamplesPerFrame();
    computeDoublesForAllZoomLevels();
    mHeightsAtThisZoomLevel = null;
}

override the draw method which draw wave on your screen.

@Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        if (mSoundFile == null)
            return;

        if (mHeightsAtThisZoomLevel == null)
            computeIntsForThisZoomLevel();

        // Draw waveform
        int measuredWidth = getMeasuredWidth();
        int measuredHeight = getMeasuredHeight();
        int start = mOffset;
        int width = mHeightsAtThisZoomLevel.length - start;
        int ctr = measuredHeight / 2;

        if (width > measuredWidth)
            width = measuredWidth;

        // Draw grid
        double onePixelInSecs = pixelsToSeconds(1);
        boolean onlyEveryFiveSecs = (onePixelInSecs > 1.0 / 50.0);
        double fractionalSecs = mOffset * onePixelInSecs;
        int integerSecs = (int) fractionalSecs;
        int i = 0;
        while (i < width) {
            i++;
            fractionalSecs += onePixelInSecs;
            int integerSecsNew = (int) fractionalSecs;
            if (integerSecsNew != integerSecs) {
                integerSecs = integerSecsNew;
                if (!onlyEveryFiveSecs || 0 == (integerSecs % 5)) {
                    canvas.drawLine(i, 0, i, measuredHeight, mGridPaint);
                }
            }
        }

        // Draw waveform
        for (i = 0; i < width; i++) {
            Paint paint;
            if (i + start >= mSelectionStart &&
                i + start < mSelectionEnd) {
                paint = mSelectedLinePaint;
            } else {
                drawWaveformLine(canvas, i, 0, measuredHeight,
                                 mUnselectedBkgndLinePaint);
                paint = mUnselectedLinePaint;
            }
            drawWaveformLine(
                canvas, i,
                ctr - mHeightsAtThisZoomLevel[start + i],
                ctr + 1 + mHeightsAtThisZoomLevel[start + i],
                paint);

            if (i + start == mPlaybackPos) {
                canvas.drawLine(i, 0, i, measuredHeight, mPlaybackLinePaint);
            }
        }

        // If we can see the right edge of the waveform, draw the
        // non-waveform area to the right as unselected
        for (i = width; i < measuredWidth; i++) {
            drawWaveformLine(canvas, i, 0, measuredHeight,
                             mUnselectedBkgndLinePaint);            
        }

        // Draw borders
        canvas.drawLine(
            mSelectionStart - mOffset + 0.5f, 30,
            mSelectionStart - mOffset + 0.5f, measuredHeight,
            mBorderLinePaint);
        canvas.drawLine(
            mSelectionEnd - mOffset + 0.5f, 0,
            mSelectionEnd - mOffset + 0.5f, measuredHeight - 30,
            mBorderLinePaint);

        // Draw timecode
        double timecodeIntervalSecs = 1.0;
        if (timecodeIntervalSecs / onePixelInSecs < 50) {
            timecodeIntervalSecs = 5.0;
        }
        if (timecodeIntervalSecs / onePixelInSecs < 50) {
            timecodeIntervalSecs = 15.0;
        }

        // Draw grid
        fractionalSecs = mOffset * onePixelInSecs;
        int integerTimecode = (int) (fractionalSecs / timecodeIntervalSecs);
        i = 0;
        while (i < width) {
            i++;
            fractionalSecs += onePixelInSecs;
            integerSecs = (int) fractionalSecs;
            int integerTimecodeNew = (int) (fractionalSecs /
                                            timecodeIntervalSecs);
            if (integerTimecodeNew != integerTimecode) {
                integerTimecode = integerTimecodeNew;

                // Turn, e.g. 67 seconds into "1:07"
                String timecodeMinutes = "" + (integerSecs / 60);
                String timecodeSeconds = "" + (integerSecs % 60);
                if ((integerSecs % 60) < 10) {
                    timecodeSeconds = "0" + timecodeSeconds;
                }
                String timecodeStr = timecodeMinutes + ":" + timecodeSeconds;
                float offset = (float) (
                    0.5 * mTimecodePaint.measureText(timecodeStr));
                canvas.drawText(timecodeStr,
                                i - offset,
                                (int)(12 * mDensity),
                                mTimecodePaint);
            }
        }

        if (mListener != null) {
            mListener.waveformDraw();
        }
    }  

Here is complete source code of Rindroid which is useful for you
Source code for waveform