ClipActivity.java

package yifeiyuan.practice.practicedemos.customview;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Region;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;

/**
 * http://ipjmc.iteye.com/blog/1299476
 */
public class ClipActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(new SampleView(ClipActivity.this));
//        setContentView(R.layout.activity_clip);
//        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
//        setSupportActionBar(toolbar);
//
//        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
//        fab.setOnClickListener(new View.OnClickListener() {
//            @Override
//            public void onClick(View view) {
//                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
//                        .setAction("Action", null).show();
//            }
//        });
    }


    private static class SampleView extends View {
        private Paint mPaint;
        private Path mPath;
        public SampleView(Context context) {
            super(context);
            setFocusable(true);

            mPaint = new Paint();
            mPaint.setAntiAlias(true);
            mPaint.setStrokeWidth(6);
            mPaint.setTextSize(16);
            mPaint.setTextAlign(Paint.Align.RIGHT);

            mPath = new Path();
        }

        private void drawScene(Canvas canvas) {
            canvas.clipRect(0, 0, 100, 100);

            canvas.drawColor(Color.WHITE);

            mPaint.setColor(Color.RED);
            canvas.drawLine(0, 0, 100, 100, mPaint);

            mPaint.setColor(Color.GREEN);
            canvas.drawCircle(30, 70, 30, mPaint);

            mPaint.setColor(Color.BLUE);
            canvas.drawText("Clipping", 100, 30, mPaint);
        }

        @Override
        protected void onDraw(Canvas canvas) {
            canvas.drawColor(Color.GRAY);
            canvas.save();
            canvas.translate(10, 10);
            drawScene(canvas);
            canvas.restore();

            canvas.save();
            canvas.translate(160, 10);
            canvas.clipRect(10, 10, 90, 90);
            canvas.clipRect(30, 30, 70, 70, Region.Op.DIFFERENCE);
            drawScene(canvas);
            canvas.restore();

            canvas.save();
            canvas.translate(10, 160);
            mPath.reset();
            canvas.clipPath(mPath); // makes the clip empty
            mPath.addCircle(50, 50, 50, Path.Direction.CCW);
            canvas.clipPath(mPath, Region.Op.REPLACE);
            drawScene(canvas);
            canvas.restore();

            canvas.save();
            canvas.translate(160, 160);
            canvas.clipRect(0, 0, 60, 60);
            canvas.clipRect(40, 40, 100, 100, Region.Op.UNION);
            drawScene(canvas);
            canvas.restore();

            canvas.save();
            canvas.translate(10, 310);
            canvas.clipRect(0, 0, 60, 60);
            canvas.clipRect(40, 40, 100, 100, Region.Op.XOR);
            drawScene(canvas);
            canvas.restore();

            canvas.save();
            canvas.translate(160, 310);
            canvas.clipRect(0, 0, 60, 60);
            canvas.clipRect(40, 40, 100, 100, Region.Op.REVERSE_DIFFERENCE);
            drawScene(canvas);
            canvas.restore();
        }
    }

}