Android的2D绘图（二）

这里面给出几个我比较喜欢的两个例子。这一节比较简单。

一、设置图像的透明度

直接看代码

package mobile.android.alpha.bitmap;

import java.io.InputStream;
import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.LinearLayout;
import android.widget.SeekBar;
import android.widget.SeekBar.OnSeekBarChangeListener;

public class Main extends Activity implements OnSeekBarChangeListener
{
	public static int alpha = 100;
	private MyView myView;

	@Override
	public void onProgressChanged(SeekBar seekBar, int progress,
			boolean fromUser)
	{
		alpha = progress;
		setTitle("alpha:" + progress);
		myView.invalidate();
	}

	@Override
	public void onStartTrackingTouch(SeekBar seekBar)
	{
		// TODO Auto-generated method stub

	}

	@Override
	public void onStopTrackingTouch(SeekBar seekBar)
	{
		// TODO Auto-generated method stub

	}

	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		LinearLayout linearLayout = new LinearLayout(this);
		linearLayout.setOrientation(LinearLayout.VERTICAL);
		myView = new MyView(this);
		myView.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT, 300));

		SeekBar seekBar = new SeekBar(this);
		seekBar.setMax(255);
		seekBar.setProgress(alpha);
		seekBar.setOnSeekBarChangeListener(this);
		linearLayout.addView(myView);
		linearLayout.addView(seekBar);
		linearLayout.setBackgroundColor(Color.WHITE);

		setContentView(linearLayout);
		setTitle("alpha:" + alpha);
	}

	private class MyView extends View
	{

		private Bitmap bitmap;

		public MyView(Context context)
		{
			super(context);
			InputStream is = getResources().openRawResource(R.drawable.image);
			bitmap = BitmapFactory.decodeStream(is);
			setBackgroundColor(Color.WHITE);
		}

		@Override
		protected void onDraw(Canvas canvas)
		{
			Paint paint = new Paint();
			paint.setAlpha(alpha);

			canvas.drawBitmap(bitmap, new Rect(0, 0, bitmap.getWidth(), bitmap
					.getHeight()), new Rect(40, 40, 200, 200), paint);

		}
	}
}

二、旋转图像

也是直接看代码

package mobile.android.rotate.anim;

import java.io.InputStream;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.os.Bundle;
import android.view.View;

public class Main extends Activity
{
	class MyView extends View
	{
		private Bitmap bitmap1;
		private Bitmap bitmap2;
		private int digree1 = 0;
		private int digree2 = 360;

		public MyView(Context context)
		{
			super(context);
			setBackgroundColor(Color.WHITE);
			InputStream is = getResources().openRawResource(R.drawable.cross);
			bitmap1 = BitmapFactory.decodeStream(is);
			
			is = getResources().openRawResource(R.drawable.ball);
			bitmap2 = BitmapFactory.decodeStream(is);
		}

		@Override  
		protected void onDraw(Canvas canvas)
		{
			Matrix matrix = new Matrix();
			if (digree1 > 360)
				digree1 = 0;
			if(digree2 < 0)
				digree2 = 360;
			
			matrix.setRotate(digree1++, 160, 240);						
			canvas.setMatrix(matrix);
			canvas.drawBitmap(bitmap1, 88, 169, null);
			matrix.setRotate(digree2--,160 , 240);
			canvas.setMatrix(matrix);  
			canvas.drawBitmap(bitmap2, 35, 115, null);
			invalidate();

		}

	}

	@Override
	public void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		setContentView(new MyView(this));
	}
}

2D绘图就到这里了，这里只是一些比较的画图，如果想要实现更加复杂的绘图，就需要进一步学习OpenGL ES技术了。