如何在Android中保存位图以用于绘画中的撤消功能

Question

我正在制作一个应用程序，在其中我可以实现撤消功能，以便获得以前的绘图行。。但我做不到。有人能帮我举个例子吗？我将不胜感激。感谢

Answer 1

制作点的堆栈（采用ArrayList），并根据动作移动位置。

参考概念https://web.archive.org/web/20201026072821/http://www.tutorialforandroid.com/2010/11/drawing-带有canvas-in-android-undoredo.html

完美的Android在api演示中为手指绘制示例添加了撤消功能

Answer 2

包括这段代码，你可以撤消、重做，也可以在绘图时更改颜色。。。

import android.app.Activity;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.graphics.Bitmap;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Button;
import com.almondmendoza.R;
import com.almondmendoza.drawings.brush.Brush;
import com.almondmendoza.drawings.brush.CircleBrush;
import com.almondmendoza.drawings.brush.PenBrush;
import java.io.File;
import java.io.FileOutputStream;
public class DrawingActivity extends Activity implements View.OnTouchListener{
    private DrawingSurface drawingSurface;
    private DrawingPath currentDrawingPath;
    private Paint currentPaint;
    private Button redoBtn;
    private Button undoBtn;
    private Brush currentBrush;
    private File APP_FILE_PATH = new File("/sdcard/TutorialForAndroidDrawings");


    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.drawing_activity);
        setCurrentPaint();
        currentBrush = new PenBrush();
        drawingSurface = (DrawingSurface) findViewById(R.id.drawingSurface);
        drawingSurface.setOnTouchListener(this);
        redoBtn = (Button) findViewById(R.id.redoBtn);
        undoBtn = (Button) findViewById(R.id.undoBtn);
        redoBtn.setEnabled(false);
        undoBtn.setEnabled(false);
    }
    private void setCurrentPaint(){
        currentPaint = new Paint();
        currentPaint.setDither(true);
        currentPaint.setColor(0xFFFFFF00);
        currentPaint.setStyle(Paint.Style.STROKE);
        currentPaint.setStrokeJoin(Paint.Join.ROUND);
        currentPaint.setStrokeCap(Paint.Cap.ROUND);
        currentPaint.setStrokeWidth(3);
    }


    public boolean onTouch(View view, MotionEvent motionEvent) {
        if(motionEvent.getAction() == MotionEvent.ACTION_DOWN){
            currentDrawingPath = new DrawingPath();
            currentDrawingPath.paint = currentPaint;
            currentDrawingPath.path = new Path();
            currentBrush.mouseDown(currentDrawingPath.path, motionEvent.getX(), motionEvent.getY());

        }else if(motionEvent.getAction() == MotionEvent.ACTION_MOVE){
            currentBrush.mouseMove( currentDrawingPath.path, motionEvent.getX(), motionEvent.getY() );
        }else if(motionEvent.getAction() == MotionEvent.ACTION_UP){
            currentBrush.mouseUp( currentDrawingPath.path, motionEvent.getX(), motionEvent.getY() );

            drawingSurface.addDrawingPath(currentDrawingPath);
            drawingSurface.isDrawing = true;
            undoBtn.setEnabled(true);
            redoBtn.setEnabled(false);
        }
        return true;
    }

    public void onClick(View view){
        switch (view.getId()){
            case R.id.colorRedBtn:
                currentPaint = new Paint();
                currentPaint.setDither(true);
                currentPaint.setColor(0xFFFF0000);
                currentPaint.setStyle(Paint.Style.STROKE);
                currentPaint.setStrokeJoin(Paint.Join.ROUND);
                currentPaint.setStrokeCap(Paint.Cap.ROUND);
                currentPaint.setStrokeWidth(3);
            break;
            case R.id.colorBlueBtn:
                currentPaint = new Paint();
                currentPaint.setDither(true);
                currentPaint.setColor(0xFF00FF00);
                currentPaint.setStyle(Paint.Style.STROKE);
                currentPaint.setStrokeJoin(Paint.Join.ROUND);
                currentPaint.setStrokeCap(Paint.Cap.ROUND);
                currentPaint.setStrokeWidth(3);
            break;
            case R.id.colorGreenBtn:
                currentPaint = new Paint();
                currentPaint.setDither(true);
                currentPaint.setColor(0xFF0000FF);
                currentPaint.setStyle(Paint.Style.STROKE);
                currentPaint.setStrokeJoin(Paint.Join.ROUND);
                currentPaint.setStrokeCap(Paint.Cap.ROUND);
                currentPaint.setStrokeWidth(3);
            break;
            case R.id.undoBtn:
                drawingSurface.undo();
                if( drawingSurface.hasMoreUndo() == false ){
                    undoBtn.setEnabled( false );
                }
                redoBtn.setEnabled( true );
            break;
            case R.id.redoBtn:
                drawingSurface.redo();
                if( drawingSurface.hasMoreRedo() == false ){
                    redoBtn.setEnabled( false );
                }
                undoBtn.setEnabled( true );
            break;
            case R.id.saveBtn:
                final Activity currentActivity  = this;
                Handler saveHandler = new Handler(){
                    @Override
                    public void handleMessage(Message msg) {
                        final AlertDialog alertDialog = new AlertDialog.Builder(currentActivity).create();
                        alertDialog.setTitle("Saved 1");
                        alertDialog.setMessage("Your drawing had been saved :)");
                        alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int which) {
                                return;
                            }
                        });
                        alertDialog.show();
                    }
                } ;
               new ExportBitmapToFile(this,saveHandler, drawingSurface.getBitmap()).execute();
            break;
            case R.id.circleBtn:
                currentBrush = new CircleBrush();
            break;
            case R.id.pathBtn:
                currentBrush = new PenBrush();
            break;
        }
    }

    private class ExportBitmapToFile extends AsyncTask<Intent,Void,Boolean> {
        private Context mContext;
        private Handler mHandler;
        private Bitmap nBitmap;
        public ExportBitmapToFile(Context context,Handler handler,Bitmap bitmap) {
            mContext = context;
            nBitmap = bitmap;
            mHandler = handler;
        }
        @Override
        protected Boolean doInBackground(Intent... arg0) {
            try {
                if (!APP_FILE_PATH.exists()) {
                    APP_FILE_PATH.mkdirs();
                }
                final FileOutputStream out = new FileOutputStream(new File(APP_FILE_PATH + "/myAwesomeDrawing.png"));
                nBitmap.compress(Bitmap.CompressFormat.PNG, 90, out);
                out.flush();
                out.close();
                return true;
            }catch (Exception e) {
                e.printStackTrace();
            }
            //mHandler.post(completeRunnable);
            return false;
        }

        @Override
        protected void onPostExecute(Boolean bool) {
            super.onPostExecute(bool);
            if ( bool ){
                mHandler.sendEmptyMessage(1);
            }
        }
    }
}