Android圖形繪製基礎(一)

mainActiviry如下:

package com.cn;import android.app.Activity;import android.os.Bundle;public class MainActivity extends Activity {     private DrawBitmapView mDrawBitmapView;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        mDrawBitmapView=new DrawBitmapView(MainActivity.this, null);        setContentView(mDrawBitmapView);    }  }

DrawBitmapView如下:

package com.cn;import android.content.Context;import android.graphics.Bitmap;import android.graphics.BitmapFactory;import android.graphics.Canvas;import android.graphics.Matrix;import android.graphics.Paint;import android.util.AttributeSet;import android.view.MotionEvent;import android.view.View;//問題0://Matrix m1=new Matrix();//注意這個類的包的引入,android.graphics.Matrix//問題1://post和set以及pre的使用//這三種都可以改變Matrix但是用法不太一樣//1.1若連續多次使用set那麼只有最後一個set起到作用//1.2常用的是第一次時用set,在隨後都採用post的方式//   表示追加.//1.3pre表示最先發生.即會在post和set前發生//問題2://Rotate預設是以(0,0)為參照點//所以常要設定參考旋轉點//m1.postRotate(30,70,100);//問題3://設定Alpha的時候//mPaint.setAlpha(30);//取值範圍為[0..255]//備忘://最好將以下測試方法,分開進行public class DrawBitmapView extends View {Bitmap mBitmap;Paint mPaint;public DrawBitmapView(Context context, AttributeSet attrs) {super(context, attrs);initView();}public void initView(){mPaint=new Paint();mBitmap=BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);}    @Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);// // ----->測試1:// //先繪製一個圖形// //然後繪製經過位移,旋轉,縮放後的圖形(方法1)// //第一次繪製// mPaint.setAntiAlias(true);// canvas.drawBitmap(mBitmap, 50, 50, mPaint);// canvas.save();// //第二次繪製// Matrix m1 = new Matrix();// m1.setTranslate(70, 100);// m1.postScale(1.5f, 1.5f);// m1.postRotate(30, 70, 100);// canvas.drawBitmap(mBitmap, m1, mPaint);//// ----->測試2://// 先繪製一個圖形//// 然後繪製經過位移,旋轉,縮放後的圖形(方法2)//// 第一次繪製//mPaint.setAntiAlias(true);//canvas.drawBitmap(mBitmap, 50, 50, mPaint);//canvas.save();//// 第二次繪製//Matrix m2 = new Matrix();//m2.setTranslate(70, 100);//m2.postScale(1.5f, 1.5f);//Matrix m3=new Matrix();//mPaint.setAlpha(50);//m3.setRotate(30, 70, 100);////利用setConcat銜接兩個變換//Matrix m4=new Matrix();//m4.setConcat(m2, m3);//canvas.drawBitmap(mBitmap, m4, mPaint);//      canvas.restore();//canvas.save();// ----->測試3:preXXX()方法和xxxSkew()方法//該類方法會在當前矩陣的最前面發生//比如在該例子中,會先旋轉後位移// 第一次繪製mPaint.setAntiAlias(true);canvas.drawBitmap(mBitmap, 50, 50, mPaint);canvas.save();// 第二次繪製Matrix m5=new Matrix();m5.setTranslate(100, 200);m5.preRotate(30, 50, 50);//skew表示傾斜m5.postSkew(0.2f, 0.2f, 50, 50);canvas.drawBitmap(mBitmap, m5, mPaint);}    @Override    public boolean onTouchEvent(MotionEvent event) {    return super.onTouchEvent(event);    }}