Develop Reference

MPAndroidChart - is it possible to control z-index of the chart elements?

I would like to have the following order of drawing in my MPAndroidChart (from bottom to top):
Data connecting line
Limit line
Data points
Is it possible? I am aware of the method com.github.mikephil.charting.components.AxisBase#setDrawLimitLinesBehindData. It is working as expected except for one case. When the Y value of all data points is the same, the effect is:
or this:
I would like it to look like:
The first 2 pictures are from MPAndroidChart Android library. The 3rd one is from iOS port of the library: Charts
I looked at the order or drawing the chart in Android and iOS versions and they look the same.
Questions:
Is it possible to control the drawing order?
What comes the difference from between system versions?
Is there any other open source library that can do that?
Additional info: all images, lines, circles are drawn by the library, custom images are not used.

Similar to a previous answer here there is no public API exposed to directly set the z-index of the various drawing features.
Instead, components are drawn in order on the canvas with later components being drawn over earlier ones. This means you change the rendering order, you can change the z-index.
You say you would like the following drawing order:
Data connecting line
Limit line
Data points
Let's find the methods in the source code that deal with each of those:
Data connecting line is drawn inside LineChartRenderer in a method called:
protected drawLinear(Canvas c, ILineDataSet dataSet)
The limit line is drawn inside XAxisRenderer called:
public void renderLimitLines(Canvas c)
The data points (circles) are drawn inside LineChartRenderer in a method that looks like this:
public void drawExtras(Canvas c)
The calling order of these three methods is determined inside BarLineChartBase in the method overriden from Android's View:
protected onDraw(Canvas canvas);
So to get the order you want you will have to simply re-arrange the order of calling of the above 3 methods inside onDraw(Canvas canvas):
Here is the complete code for a custom line chart that should meet the requirement. By design, you will still have to call:
com.github.mikephil.charting.components.AxisBase#setDrawLimitLinesBehindData
But you could easily remove the 3 if statements and hard-code the order should you so desire.
CustomZIndexBarLineBase.java
import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import com.github.mikephil.charting.charts.BarLineChartBase;
import com.github.mikephil.charting.data.LineData;
/**
* Created by David on 11/01/2017.
*/
public class CustomZIndexLineChartBase extends BarLineChartBase<LineData> {
public CustomZIndexLineChartBase(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public CustomZIndexLineChartBase(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CustomZIndexLineChartBase(Context context) {
super(context);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
if (mData == null)
return;
// execute all drawing commands
drawGridBackground(canvas);
if (mAxisLeft.isEnabled())
mAxisRendererLeft.computeAxis(mAxisLeft.mAxisMinimum, mAxisLeft.mAxisMaximum, mAxisLeft.isInverted());
if (mAxisRight.isEnabled())
mAxisRendererRight.computeAxis(mAxisRight.mAxisMinimum, mAxisRight.mAxisMaximum, mAxisRight.isInverted());
if (mXAxis.isEnabled())
mXAxisRenderer.computeAxis(mXAxis.mAxisMinimum, mXAxis.mAxisMaximum, false);
mXAxisRenderer.renderAxisLine(canvas);
mAxisRendererLeft.renderAxisLine(canvas);
mAxisRendererRight.renderAxisLine(canvas);
if (mAutoScaleMinMaxEnabled) {
autoScale();
}
mXAxisRenderer.renderGridLines(canvas);
mAxisRendererLeft.renderGridLines(canvas);
mAxisRendererRight.renderGridLines(canvas);
if (mXAxis.isDrawLimitLinesBehindDataEnabled())
mXAxisRenderer.renderLimitLines(canvas);
if (mAxisLeft.isDrawLimitLinesBehindDataEnabled())
mAxisRendererLeft.renderLimitLines(canvas);
if (mAxisRight.isDrawLimitLinesBehindDataEnabled())
mAxisRendererRight.renderLimitLines(canvas);
int clipRestoreCount = canvas.save();
canvas.clipRect(mViewPortHandler.getContentRect());
mRenderer.drawData(canvas); //NOTE: draws line between points
if (valuesToHighlight())
mRenderer.drawHighlighted(canvas, mIndicesToHighlight);
canvas.restoreToCount(clipRestoreCount);
//NOTE: draws limit line
if (!mXAxis.isDrawLimitLinesBehindDataEnabled())
mXAxisRenderer.renderLimitLines(canvas);
if (!mAxisLeft.isDrawLimitLinesBehindDataEnabled())
mAxisRendererLeft.renderLimitLines(canvas);
if (!mAxisRight.isDrawLimitLinesBehindDataEnabled())
mAxisRendererRight.renderLimitLines(canvas);
mRenderer.drawExtras(canvas); //NOTE: draws circles
mXAxisRenderer.renderAxisLabels(canvas);
mAxisRendererLeft.renderAxisLabels(canvas);
mAxisRendererRight.renderAxisLabels(canvas);
if (isClipValuesToContentEnabled()) {
clipRestoreCount = canvas.save();
canvas.clipRect(mViewPortHandler.getContentRect());
mRenderer.drawValues(canvas);
canvas.restoreToCount(clipRestoreCount);
} else {
mRenderer.drawValues(canvas);
}
mLegendRenderer.renderLegend(canvas);
drawDescription(canvas);
drawMarkers(canvas);
}
}
CustomZIndexLineChart.java
import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import com.github.mikephil.charting.data.LineData;
import com.github.mikephil.charting.interfaces.dataprovider.LineDataProvider;
import com.github.mikephil.charting.renderer.LineChartRenderer;
/**
* Created by David on 11/01/2017.
*/
public class CustomZIndexLineChart extends CustomZIndexLineChartBase implements LineDataProvider {
public CustomZIndexLineChart(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public CustomZIndexLineChart(Context context, AttributeSet attrs) {
super(context, attrs);
}
public CustomZIndexLineChart(Context context) {
super(context);
}
#Override
protected void init() {
super.init();
mRenderer = new LineChartRenderer(this, mAnimator, mViewPortHandler);
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
}
#Override
public LineData getLineData() {
return mData;
}
#Override
protected void onDetachedFromWindow() {
// releases the bitmap in the renderer to avoid oom error
if (mRenderer != null && mRenderer instanceof LineChartRenderer) {
((LineChartRenderer) mRenderer).releaseBitmap();
}
super.onDetachedFromWindow();
}
}

What triggers a call to AccessibilityInteractionController.performAccessibilityActionUiThread on Android?

There is a crash on a Samsung Galaxy S 7 Edge when a user is interacting with an EditText that has a LengthFilter InputFilter applied. How would a user cause the method AccessibilityInteractionController.performAccessibilityActionUiThread to be called?
I looked at the source of AccessibilityInteractionController but I cannot find good documentation of how a user would trigger that method.
My crash's stack trace is similar to what is posted in these questions:
Android exception - Unknown origin (possibly widget)
My Android App has IndexOutOfBoundsException,how to solved?

Looking into Android's issue tracker, it seems that this issue is due to password managers using Accessibility events to generate passwords. However, generated password don't respect the maxLength property, causing the crash.
The suggested solution seems to work: creating a subclass, and using that instead. (Copying the code for reference)
public class SafePinEntryEditText extends EditText {
public SafePinEntryEditText(Context context) {
super(context);
}
public SafePinEntryEditText(Context context, AttributeSet attrs) {
super(context, attrs);
}
public SafePinEntryEditText(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
}
#TargetApi(21)
public SafePinEntryEditText(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
#Override
public void setSelection(int index) {
// prevent index out of bounds caused by AccessibilityService events
if (index > length()) {
index = length();
}
super.setSelection(index);
}
#Override
public void setSelection(int start, int stop) {
// prevent index out of bounds caused by AccessibilityService events
if (start > length()) {
start = length();
}
if (stop > length()) {
stop = length();
}
super.setSelection(start, stop);
}
}

Android - findViewById returns null

I'm following an example from a book and I can't understand why findViewById returns null.
This is my activity:
package it.mt.compass;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Toast;
public class CompassActivity extends Activity {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
CompassView cv = (CompassView)this.findViewById(R.id.compassView1);
// this crashes the application
//cv.setBearing(45);
// some debug code
Toast test_result;
if(cv == null) {
test_result = Toast.makeText(this, "1", Toast.LENGTH_SHORT);
test_result.show();
}
else {
test_result = Toast.makeText(this, "0", Toast.LENGTH_SHORT);
test_result.show();
}
// it shows 1
}
}
and this is the res/layout/main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<it.mt.compass.CompassView
android:id="#+id/compassView1"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</LinearLayout>
Already cleaned (as suggested in other similar topics; what does "Clean" do?) the project with no luck.
Many thanks in advance.
Mirko
As requested, the constructors' code:
// Constructors
public CompassView(Context context) {
super(context);
initCompassView();
}
public CompassView(Context context, AttributeSet attrs) {
super(context);
initCompassView();
}
public CompassView(Context context, AttributeSet ats, int defaultStyle) {
super(context);
initCompassView();
}
That's the correct version (the problem was I didn't passed the parameters correctly to the superclass constructor):
// Constructors
public CompassView(Context context) {
super(context);
initCompassView();
}
public CompassView(Context context, AttributeSet attrs) {
super(context, attrs);
initCompassView();
}
public CompassView(Context context, AttributeSet ats, int defaultStyle) {
super(context, ats, defaultStyle);
initCompassView();
}

CompassView constructor implementation is incorrect. You're not passing the attributes to superclass and hence the id is lost.
Change here the superclass constructor invocation
public CompassView(Context context, AttributeSet attrs) {
super(context);
to super(context, attrs);
and
public CompassView(Context context, AttributeSet ats, int defaultStyle) {
super(context);
to super(context, attrs, defaultStyle); if the superclass has a ctor that accepts three args. Otherwise just use super(context, attrs). Oh, and rename the arg name from ats, even though the name doesn't matter.

In eclipse do:
Projects -> Clean.
Eefresh your app.
Run.
this will clear generated old R class.

I would try closing eclipse completely and then open it again. I've seen some really bizarre things like this happening. Another way you can try this is to just add a "textView" and try to do a findById on that and see if it's returning null. You could be loading the wrong xml view..
ie: your are loading a layout from one directory but it's actually loading a different view in a different directory with the same name...

add import it.mt.compass.R;
and try another View, like a Image or TextView instead

NumberFormatException with IntEditTextPreference

In my android application, I'm using a class called 'IntEditTextPreference'. This class is used when I want a user to introduce a preference as an integer.
But it has a problem. When the user leaves the field empty and press "ok", an NumberFormatException is thrown.
What could I do to avoid the user to press "ok" when the field is empty?
Thanks!
public class IntEditTextPreference extends EditTextPreference
{
public IntEditTextPreference(Context context)
{
super(context);
}
public IntEditTextPreference(Context context, AttributeSet attrs)
{
super(context, attrs);
}
public IntEditTextPreference(Context context, AttributeSet attrs, int defStyle)
{
super(context, attrs, defStyle);
}
#Override
protected String getPersistedString(String defaultReturnValue)
{
return String.valueOf(getPersistedInt(-1));
}
#Override
protected boolean persistString(String value)
{
return persistInt(Integer.valueOf(value));
}
}

You should probably still have a try/catch block around it to catch NumberFormatException. But there are many ways to do this. One way is you can use the buttons setClickable method to false and then true when the text is not null and is integer using onTextChangedListener. Or you could simply let it be clickable but check for empty string or non-integer when the button is clicked and use a warning message toast/alert/label to let the user know they have incorrect field before allowing the button to do anything else. Hope this helps!

In general if you are using a browser-based-application, you would use JavaScript/AJAX to display a button when the input is valid. This is already handled at client side.
To avoid the NumberFormatException, simply add a try-catch-block around the Integer.valueOf(value) statement.
Basically it depends on your client-framework. There might be better framework-specific solutions. Which one do you use?

Android drawing cache

Please explain how does the drawing cache work in Android. I'm implementing a custom View subclass. I want my drawing to be cached by the system. In the View constructor, I call
setDrawingCacheEnabled(true);
Then in the draw(Canvas c), I do:
Bitmap cac = getDrawingCache();
if(cac != null)
{
c.drawBitmap(cac, 0, 0, new Paint());
return;
}
Yet the getDrawingCache() returns null to me. My draw() is not called neither from setDrawingCacheEnabled(), nor from getDrawingCache(). Please, what am I doing wrong?

There's a hard limit on drawing cache size, available via the ViewConfiguration class.. My view is larger than allowed for caching.
FYI, the sources of the View class are available via the SDK Manager for some (not all) Android versions.

Hopefully this explains it.
public class YourCustomView extends View {
private String mSomeProperty;
public YourCustomView(Context context) {
super(context);
}
public YourCustomView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public YourCustomView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public void setSomeProperty(String value) {
mSomeProperty = value;
setDrawingCacheEnabled(false); // clear the cache here
invalidate();
}
#Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// specific draw logic here
setDrawingCacheEnabled(true); // cache
}
#Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
...
}
}
Example code explained.
In the setSomeProperty() method call setDrawingCacheEnabled(false) to clear the cache and force a redraw by calling invalidate().
Call setDrawingCacheEnabled(true) in the onDraw method after drawing to the canvas.
Optionally place a log statement in the onDraw method to confirm it is only called once each time you call the setSomeProperty() method. Be sure to remove the log call once confirmed as this will become a performance issue.