android 加载图片并在上面画图

像Ps上的应用一样，我们加载一个图片然后在上面增加各种我们需要的挂件，文字效果等。我们今天完成一个简单的Demo

package com.example.fingerdraw;import java.io.FileNotFoundException;import java.io.OutputStream;import android.app.Activity;import android.content.ContentValues;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.provider.MediaStore.Images.Media;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;public class MainActivity extends Activity implements OnTouchListener,        OnClickListener {    private ImageView image;    private Paint paint;    private Canvas canvas;    private Bitmap bitmap;    private Bitmap alterBitmap;    private Button choose;    private Button save;    private final static int RESULT = 0;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        image = (ImageView) findViewById(R.id.image);        choose = (Button) findViewById(R.id.chooseButton);        save=(Button)findViewById(R.id.saveButton);        /*         * bitmap = Bitmap.createBitmap(getWindowManager().getDefaultDisplay()         * .getWidth(), getWindowManager().getDefaultDisplay().getHeight(),         * Bitmap.Config.ARGB_8888); canvas = new Canvas(bitmap);// 画板 paint =         * new Paint();// 画刷 paint.setColor(Color.BLUE);         * image.setImageBitmap(bitmap);         */        image.setOnTouchListener(this);        choose.setOnClickListener(this);        save.setOnClickListener(this);    }    private float downx = 0;    private float downy = 0;    private float upx = 0;    private float upy = 0;    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:            // 路径画板            upx = event.getX();            upy = event.getY();            canvas.drawLine(downx, downy, upx, upy, paint);            image.invalidate();            downx = upx;            downy = upy;            break;        case MotionEvent.ACTION_UP:            // 直线画板            upx = event.getX();            upy = event.getY();            canvas.drawLine(downx, downy, upx, upy, paint);            image.invalidate();// 刷新            break;        default:            break;        }        return true;    }    public void onClick(View arg0) {        if(arg0==choose){        Intent intent = new Intent(Intent.ACTION_PICK,                android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);        startActivityForResult(intent, RESULT);        }else if(arg0==save){            //保存画好的图片            if(alterBitmap!=null){                try {                    Uri imageUri=getContentResolver().insert(Media.EXTERNAL_CONTENT_URI, new ContentValues());                    OutputStream outputStream=getContentResolver().openOutputStream(imageUri);                    alterBitmap.compress(CompressFormat.PNG, 90, outputStream);                    Toast.makeText(getApplicationContext(), "save!", Toast.LENGTH_SHORT).show();                } catch (FileNotFoundException e) {                    e.printStackTrace();                }            }        }    }    @Override    protected void onActivityResult(int requestCode, int resultCode, Intent data) {        // TODO Auto-generated method stub        super.onActivityResult(requestCode, resultCode, data);        if (resultCode == RESULT_OK) {            Uri imageFileUri = data.getData();            Display display = getWindowManager().getDefaultDisplay();            float dw = display.getWidth();            float dh = display.getHeight();            try {                BitmapFactory.Options options = new BitmapFactory.Options();                options.inJustDecodeBounds = true;                bitmap = BitmapFactory.decodeStream(getContentResolver()                        .openInputStream(imageFileUri), null, options);                int heightRatio = (int) Math.ceil(options.outHeight / dh);                int widthRatio = (int) Math.ceil(options.outWidth / dw);                if (heightRatio > 1 && widthRatio > 1) {                    if (heightRatio > widthRatio) {                        options.inSampleSize = heightRatio;                    } else {                        options.inSampleSize = widthRatio;                    }                }                options.inJustDecodeBounds = false;                bitmap = BitmapFactory.decodeStream(getContentResolver()                        .openInputStream(imageFileUri), null, options);                alterBitmap = Bitmap.createBitmap(bitmap.getWidth(),                        bitmap.getHeight(), bitmap.getConfig());                canvas = new Canvas(alterBitmap);                paint = new Paint();                paint.setColor(Color.GREEN);                paint.setStrokeWidth(10);                Matrix matrix = new Matrix();                canvas.drawBitmap(bitmap, matrix, paint);                image.setImageBitmap(alterBitmap);                image.setOnTouchListener(this);            } catch (FileNotFoundException e) {                e.printStackTrace();            }        }    }}



效果：

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