Android手指绘图(一)

package cn.c;
import java.io.OutputStream;
import android.app.Activity;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Bitmap.CompressFormat;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Matrix;
import android.graphics.Paint;
import android.net.Uri;
import android.os.Bundle;
import android.view.Display;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.View.OnTouchListener;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;
/**
 * 注意:
 * 1 event.getX()和event.getRawX()方法的区别
 *   event.getX()是相对于父控件而言
 *   event.getRawX()是相对于屏幕左上角而言
 * 2 在Activity中处理触摸事件采用的是OnTouchEvent()
 *   在View中处理触摸事件是实现OnTouchListener{}接口
 *   覆写其中的onTouch()方法
 * 3 Bug的问题:
 *   计算options.inSampleSize这里有Bug.有的图片过大在
 *   设备图片库中是被旋转处理了的(虽然看上去没有).比如一
 *   张大图片在图片库中看上去是竖屏的,但得到后在ImageView
 *   中显示却是横屏的.
 *   所以这里方便测试直接:
 *   options.inSampleSize=8;
 *   写死了
 * 4 调用bitmap.compress()方法的时候注意若设置格式为PNG,那么则无效.
 *   因为PNG将始终保持所有数据.JPEG是"有损的"编解码器
 */
public class MainActivity extends Activity implements OnTouchListener{
    private ImageView mImageView;
    private Button mButton;
    private Button mSaveButton;
    private Bitmap mRawBitmap;
    private Bitmap mAlteredBitmap;
    private Paint mPaint;
    private Canvas mCanvas;
    private Uri mPhotoFileUri;
    private final int PICK=88;
    float downX=0;
    float downY=0;
    float upX=0;
    float upY=0;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        mImageView=(ImageView) findViewById(R.id.imageView);
        mImageView.setOnTouchListener(this);
        mButton=(Button) findViewById(R.id.button);
        mButton.setOnClickListener(new ButtonOnClickListener());
        mSaveButton=(Button) findViewById(R.id.saveButton);
        mSaveButton.setOnClickListener(new ButtonOnClickListener());
        mPaint=new Paint();
        mPaint.setColor(Color.RED);
        mPaint.setStrokeWidth(5);
    }

	@Override
	protected void onActivityResult(int requestCode, int resultCode, Intent data) {
		super.onActivityResult(requestCode, resultCode, data);
		if (requestCode==PICK) {
			mPhotoFileUri=data.getData();
			Display display=getWindowManager().getDefaultDisplay();
			float w=display.getWidth();
			float h=display.getHeight();
			try {
				BitmapFactory.Options  options=new BitmapFactory.Options();
				options.inJustDecodeBounds=true;
				mRawBitmap=BitmapFactory.decodeStream
			    (getContentResolver().openInputStream(mPhotoFileUri), null, options);
				int widthRation=(int) Math.ceil(options.outHeight/h);
				int heightRation=(int) Math.ceil(options.outWidth/w);
				if (heightRation>1&&widthRation>1) {
					if (heightRation>widthRation) {
						options.inSampleSize=heightRation;
					} else {
						options.inSampleSize=widthRation;
					}
				}
				//Bug所在:
				options.inSampleSize=8;
				options.inJustDecodeBounds=false;
				mRawBitmap=BitmapFactory.decodeStream
			   (getContentResolver().openInputStream(mPhotoFileUri), null, options);
				mAlteredBitmap=Bitmap.createBitmap
				(mRawBitmap.getWidth(), mRawBitmap.getHeight(), mRawBitmap.getConfig());
				mCanvas=new Canvas(mAlteredBitmap);
				Matrix matrix=new Matrix();
				mCanvas.drawBitmap(mRawBitmap, matrix, mPaint);
				mImageView.setImageBitmap(mAlteredBitmap);
			} catch (Exception e) {
			}
		}
	}

	private class ButtonOnClickListener implements OnClickListener {
		public void onClick(View v) {
			switch (v.getId()) {
			case R.id.button:
				Intent intent = new Intent(
				Intent.ACTION_PICK,
				android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
				startActivityForResult(intent, PICK);
				break;
			case R.id.saveButton:
				try {
					if (mPhotoFileUri!=null) {
						OutputStream fos=getContentResolver().openOutputStream(mPhotoFileUri);
						mAlteredBitmap.compress(CompressFormat.JPEG, 90, fos);
						fos.close();
						Toast.makeText(MainActivity.this, "OK", Toast.LENGTH_SHORT).show();
					}

				} catch (Exception e) {
					// TODO: handle exception
				}

				break;
			default:
				break;
			}

		}

	}

	public boolean onTouch(View v, MotionEvent event) {
		int action = event.getAction();
		switch (action) {
		case MotionEvent.ACTION_DOWN:
            downX=event.getX();
            downY=event.getY();
			break;
		case MotionEvent.ACTION_MOVE:
			upX=event.getX();
            upY=event.getY();
            mCanvas.drawLine(downX, downY, upX, upY, mPaint);
            mImageView.invalidate();
            downX=upX;
            downY=upY;
			break;
		case MotionEvent.ACTION_UP:
//            upX=event.getX();
//            upY=event.getY();
//            mCanvas.drawLine(downX, downY, upX, upY, mPaint);
//            mImageView.invalidate();
			break;
		case MotionEvent.ACTION_CANCEL:
			break;

		default:
			break;
		}
		return true;
	}

}