layout - Modifying the Android seekbar widget to operate vertically

Question

I'm trying to get a vertical seekbar going with the emulator, but I'm sort of stuck. I can get the seekbar to display the way I want it to, and I can get the progress to do what I want, and I can modify the onTouchEvent to get the thumb to go vertically instead of horizontally. What I can't do is get the thumb to move outside of the default 29 horizontal pixels without using setThumbOffset(). This in itself isn't a problem. The problem is coming from the fact that I don't understand the thumbOffset at all -- I guess. I think I could (properly) resize the widget, which I am pretty sure I'm not doing right. Or maybe I could just use the thumbOffset if I could figure it out. Since I can calculate the progress correctly I thought I would just use a linear function of progress * (getTop() - getBottom()) of the widget but that doesn't seem to do it. But I can't figure out what the offset is centered around.

As a somewhat aside, I am really unsure if what I am doing in onSizeChanged() is sane or if it's going to bite me in the ass later on.

Here's the main.xml layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <com.mobilsemantic.mobipoll.SlideBar
        android:id="@+id/slide"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:max="100"
        android:progress="0"
        android:secondaryProgress="25" />

        <Button android:id="@+id/button"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:text="Hello, I am a Button" />

    <TextView android:id="@+id/tracking"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

And the class (ignore the debugging junk):

import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.widget.SeekBar;

public class SlideBar extends SeekBar {

        private int oHeight = 320, oWidth = 29;
        private int oProgress = -1, oOffset = -1;;
        private float xPos = -1, yPos = -1;
        private int top = -1, bottom = -1, left = -1, right = -1;

        public SlideBar(Context context) {
                super(context);
        }
        public SlideBar(Context context, AttributeSet attrs)
        {
                super(context, attrs);
                oOffset = this.getThumbOffset();
                oProgress = this.getProgress();
        }
        public SlideBar(Context context, AttributeSet attrs, int defStyle)
        {
                super(context, attrs, defStyle);
        }

        protected synchronized void onMeasure(int widthMeasureSpec, intheightMeasureSpec)
        {
                int height = View.MeasureSpec.getSize(heightMeasureSpec);
                oHeight = height;
                this.setMeasuredDimension(oWidth, oHeight);

        }
        protected void onSizeChanged(int w, int h, int oldw, int oldh)
        {
                super.onSizeChanged(h, w, oldw, oldh);
        }
        protected void onLayout(boolean changed, int l, int t, int r, int b)
        {
                super.onLayout(changed, l, t, r, b);
                left = l;
                right = r;
                top = t;
                bottom = b;
        }
        protected void onDraw(Canvas c)
        {
                c.rotate(90);
                c.translate(0,-29);
                super.onDraw(c);
        }
        public boolean onTouchEvent(MotionEvent event)
        {
                xPos = event.getX();
                yPos = event.getY();
                float progress = (yPos-this.getTop())/(this.getBottom()-this.getTop());
                oOffset = this.getThumbOffset();
                oProgress = this.getProgress();
                Log.d("offset" + System.nanoTime(), new Integer(oOffset).toString());
                Log.d("progress" + System.nanoTime(), new Integer(oProgress).toString());

                float offset;

                offset = progress * (this.getBottom()-this.getTop());

                this.setThumbOffset((int)offset);

                Log.d("offset_postsetprogress" + System.nanoTime(), new Integer(oOffset).toString());
                Log.d("progress_postsetprogress" + System.nanoTime(), new Integer(oProgress).toString());

                this.setProgress((int)(100*event.getY()/this.getBottom()));
                return true;
        }

}

Answer 1

I've created a solution which works (at least for me, anyway) and creates a vertical SeekBar. http://hackskrieg.wordpress.com/2012/04/20/working-vertical-seekbar-for-android/

This code will correctly select/deselect the thumb, move correctly, update the listener correctly (only when the progress changes!), update/draw the progress correctly, etc. I hope it helps you.

public class VerticalSeekBar extends SeekBar {

public VerticalSeekBar(Context context) {
    super(context);
}

public VerticalSeekBar(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}

public VerticalSeekBar(Context context, AttributeSet attrs) {
    super(context, attrs);
}

protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(h, w, oldh, oldw);
}

@Override
protected synchronized void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(heightMeasureSpec, widthMeasureSpec);
    setMeasuredDimension(getMeasuredHeight(), getMeasuredWidth());
}

protected void onDraw(Canvas c) {
    c.rotate(-90);
    c.translate(-getHeight(), 0);

    super.onDraw(c);
}

private OnSeekBarChangeListener onChangeListener;
@Override
public void setOnSeekBarChangeListener(OnSeekBarChangeListener onChangeListener){
    this.onChangeListener = onChangeListener;
}

private int lastProgress = 0;
@Override
public boolean onTouchEvent(MotionEvent event) {
    if (!isEnabled()) {
        return false;
    }

    switch (event.getAction()) {
    case MotionEvent.ACTION_DOWN:
        onChangeListener.onStartTrackingTouch(this);
        setPressed(true);
        setSelected(true);
        break;
    case MotionEvent.ACTION_MOVE:
        // Calling the super seems to help fix drawing problems
        super.onTouchEvent(event);
        int progress = getMax() - (int) (getMax() * event.getY() / getHeight());

        // Ensure progress stays within boundaries of the seekbar
        if(progress < 0) {progress = 0;}
        if(progress > getMax()) {progress = getMax();}

        // Draw progress
        setProgress(progress);

        // Only enact listener if the progress has actually changed
        // Otherwise the listener gets called ~5 times per change
        if(progress != lastProgress) {
            lastProgress = progress;
            onChangeListener.onProgressChanged(this, progress, true);
        }

        onSizeChanged(getWidth(), getHeight() , 0, 0);
        onChangeListener.onProgressChanged(this, getMax() - (int) (getMax() * event.getY() / getHeight()), true);
        setPressed(true);
        setSelected(true);
        break;
    case MotionEvent.ACTION_UP:
        onChangeListener.onStopTrackingTouch(this);
        setPressed(false);
        setSelected(false);
        break;
    case MotionEvent.ACTION_CANCEL:
        super.onTouchEvent(event);
        setPressed(false);
        setSelected(false);
        break;
    }
    return true;
}

public synchronized void setProgressAndThumb(int progress) {
    setProgress(getMax() - (getMax()- progress));
    onSizeChanged(getWidth(), getHeight() , 0, 0);
}

public synchronized void setMaximum(int maximum) {
    setMax(maximum);
}

public synchronized int getMaximum() {
    return getMax();
}
}

I just placed this vertical SeekBar inside a LinearLayout with layout_height set to FILL_PARENT and layout_width set to WRAP_CONTENT.

<LinearLayout
    android:layout_width="wrap_content"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <com.safetyculture.jsadroidtablet.VerticalSeekBar
        android:id="@+id/calculatorVerticalSeekBar"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:layout_gravity="bottom"
        android:max="4"
        android:progress="2" />

</LinearLayout>

NOTE: You must set an OnSeekBarChangeListener, otherwise interacting with the SeekBar will produce NullPointerException.