How to draw Arcs in Android using canvas?
This is a simple example showing how to draw Arcs in android, You can use this to create piecharts or someother similar thing you want.
Here we have 3 classes.
1. GraphicsActivity.java
2. MainActivity.java
3. PictureLayout.java
GraphicsActivity.java
package com.coderzheaven.arcdrawing;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
class GraphicsActivity extends Activity {
// set to true to test Picture
private static final boolean TEST_PICTURE = false;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public void setContentView(View view) {
if (TEST_PICTURE) {
ViewGroup vg = new PictureLayout(this);
vg.addView(view);
view = vg;
}
super.setContentView(view);
}
}
PictureLayout.java
package com.coderzheaven.arcdrawing;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Picture;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewParent;
public class PictureLayout extends ViewGroup {
private final Picture mPicture = new Picture();
public PictureLayout(Context context) {
super(context);
}
public PictureLayout(Context context, AttributeSet attrs) {
super(context, attrs);
}
@Override
public void addView(View child) {
if (getChildCount() > 1) {
throw new IllegalStateException("PictureLayout can host only one direct child");
}
super.addView(child);
}
@Override
public void addView(View child, int index) {
if (getChildCount() > 1) {
throw new IllegalStateException("PictureLayout can host only one direct child");
}
super.addView(child, index);
}
@Override
public void addView(View child, LayoutParams params) {
if (getChildCount() > 1) {
throw new IllegalStateException("PictureLayout can host only one direct child");
}
super.addView(child, params);
}
@Override
public void addView(View child, int index, LayoutParams params) {
if (getChildCount() > 1) {
throw new IllegalStateException("PictureLayout can host only one direct child");
}
super.addView(child, index, params);
}
@Override
protected LayoutParams generateDefaultLayoutParams() {
return new LayoutParams(LayoutParams.MATCH_PARENT, LayoutParams.MATCH_PARENT);
}
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
final int count = getChildCount();
int maxHeight = 0;
int maxWidth = 0;
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
measureChild(child, widthMeasureSpec, heightMeasureSpec);
}
}
maxWidth += getPaddingLeft() + getPaddingRight();
maxHeight += getPaddingTop() + getPaddingBottom();
Drawable drawable = getBackground();
if (drawable != null) {
maxHeight = Math.max(maxHeight, drawable.getMinimumHeight());
maxWidth = Math.max(maxWidth, drawable.getMinimumWidth());
}
setMeasuredDimension(resolveSize(maxWidth, widthMeasureSpec),
resolveSize(maxHeight, heightMeasureSpec));
}
private void drawPict(Canvas canvas, int x, int y, int w, int h,
float sx, float sy) {
canvas.save();
canvas.translate(x, y);
canvas.clipRect(0, 0, w, h);
canvas.scale(0.5f, 0.5f);
canvas.scale(sx, sy, w, h);
canvas.drawPicture(mPicture);
canvas.restore();
}
@Override
protected void dispatchDraw(Canvas canvas) {
super.dispatchDraw(mPicture.beginRecording(getWidth(), getHeight()));
mPicture.endRecording();
int x = getWidth()/2;
int y = getHeight()/2;
if (false) {
canvas.drawPicture(mPicture);
} else {
drawPict(canvas, 0, 0, x, y, 1, 1);
drawPict(canvas, x, 0, x, y, -1, 1);
drawPict(canvas, 0, y, x, y, 1, -1);
drawPict(canvas, x, y, x, y, -1, -1);
}
}
@Override
public ViewParent invalidateChildInParent(int[] location, Rect dirty) {
location[0] = getLeft();
location[1] = getTop();
dirty.set(0, 0, getWidth(), getHeight());
return getParent();
}
@Override
protected void onLayout(boolean changed, int l, int t, int r, int b) {
final int count = super.getChildCount();
for (int i = 0; i < count; i++) {
final View child = getChildAt(i);
if (child.getVisibility() != GONE) {
final int childLeft = getPaddingLeft();
final int childTop = getPaddingTop();
child.layout(childLeft, childTop,
childLeft + child.getMeasuredWidth(),
childTop + child.getMeasuredHeight());
}
}
}
}
MainActivity.java
package com.coderzheaven.arcdrawing;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Paint.Style;
import android.graphics.RectF;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.LinearLayout;
public class MainActivity extends GraphicsActivity implements OnClickListener {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
Button b1 = (Button) findViewById(R.id.button1);
Button b2 = (Button) findViewById(R.id.button2);
Button b3 = (Button) findViewById(R.id.button3);
b1.setOnClickListener(this);
b2.setOnClickListener(this);
b3.setOnClickListener(this);
}
@Override
public void onClick(View v) {
int id = v.getId();
Style sytle = null;
boolean use_centre = false;
final LinearLayout r1 = (LinearLayout) findViewById(R.id.l1);
if (MainActivity.this.findViewById(1) != null)
r1.removeView(MainActivity.this.findViewById(1));
switch (id) {
case R.id.button1:
use_centre = true;
sytle = Paint.Style.FILL;
break;
case R.id.button2:
use_centre = false;
sytle = Paint.Style.STROKE;
break;
case R.id.button3:
use_centre = true;
sytle = Paint.Style.STROKE;
break;
default:
break;
}
SampleView s = new SampleView(MainActivity.this);
s.setId(1);
s.startDraw(sytle, use_centre);
r1.addView(s);
}
private static class SampleView extends View {
private Paint mPaint;
private Paint mFramePaint;
private RectF mBigOval;
private float mStart;
private float mSweep;
private boolean use_centre = false;
private static final float SWEEP_INC = 0.5f;
private static final float START_INC = 15;
public SampleView(Context context) {
super(context);
mPaint = new Paint();
mPaint.setAntiAlias(true);
mPaint.setColor(0x880000FF);
mPaint.setStrokeWidth(4);
mBigOval = new RectF(40, 10, 280, 250);
mFramePaint = new Paint();
mFramePaint.setAntiAlias(true);
mFramePaint.setStrokeWidth(4);
}
public void startDraw(Style style, boolean use_centre) {
this.use_centre = use_centre;
mPaint.setStyle(style);
mFramePaint.setStyle(style);
}
private void drawArcs(Canvas canvas, RectF oval, boolean useCenter,
Paint paint) {
// canvas.drawRect(oval, mFramePaint);
canvas.drawArc(oval, mStart, mSweep, useCenter, paint);
}
@Override
protected void onDraw(Canvas canvas) {
canvas.drawColor(Color.WHITE);
drawArcs(canvas, mBigOval, use_centre, mPaint);
mSweep += SWEEP_INC;
if (mSweep > 360) {
mSweep -= 360;
mStart += START_INC;
if (mStart >= 360) {
mStart -= 360;
}
}
invalidate();
}
}
}
Download the complete source code from here.
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