如何更新画布绘制文本而不是重绘画布

Question

我现在可以在运动视图上的画布上绘制文本，问题是当我绘制文本并在同一画布上进行下一次绘制时，我的绘制文本正在消失我的意思是屏幕正在重绘，因为我想要的无效保留我之前的绘图并在同一个画布上进行新的绘图我将如何做到这一点？

@Override
   protected void onDraw(Canvas canvas) {
    Paint hint = new Paint();
    path = new Path();
    mTextPaths = new ArrayList<Path>();
    Log.v("getting mtextpaths", mTextPaths.toString());

    int m;
    if (strgettile != null) {
        for (m = 0; m < strgettile.length(); m++) {
            System.out.println(strgettile.charAt(m));
            char convertst = strgettile.charAt(m);
            characterToString = Character.toString(convertst);

            // canvas.drawText(characterToString, x, y, hint);
            // canvas.drawText(characterToString, m
            // * width + x, m * height + y, foreground); //its working in
            // cross
            // canvas.drawText(characterToString, x, m * height + y,
            // foreground); //its working for vertical
            // canvas.drawText(characterToString, m
            // * width + x, y, foreground); //its working in horizontal
            // setSelectedTile(tile);
            if (getorientation.equalsIgnoreCase("Horizontal")) {
                canvas.drawText(characterToString, m * width + positionX,
                        positionY, foreground); // for motion event
                hint.setColor(Color.BLACK);
                hint.setTextSize(45);
                foreground.getTextPath(characterToString, 0,
                        characterToString.length(), positionX * 2 / 3,
                        positionY - 4, path);

            } else {
                canvas.drawText(characterToString, positionX, m * height
                        + positionY, foreground);
                hint.setColor(Color.BLACK);
                hint.setTextSize(45);
                foreground.getTextPath(characterToString, 0,
                        characterToString.length(), positionX * 2 / 3,
                        positionY - 4, path);


            }


        }

    }

  public void setSelectedTile(String tile, String strorientations) {
    // TODO Auto-generated method stub
    Log.v("getting string in puzzle view ", tile);
    strgettile = tile;
    getorientation = strorientations;
    mTextPaths.add(path);
    invalidate();


}

Answer 1

1. 每当您调用 无效（）方法。所以我正在维护所有的文本和位置 在 arraylist 中并在每次单击画布时绘制画布。

2. 这是解决您的问题的方法之一。画布只是一个 位图。无论你在上面画什么都是永久的。有办法 处理它，但大多数实现只是重绘整个 每次通过画布。

   以下是代码片段：

   public class PuzzleView extends View {
   private static final String TAG = "Sudoku";
   private float width; // width of one tile
   private float height; // height of one tile
   private int selX; // X index of selection
   private int selY; // Y index of selection
   private final Rect selRect = new Rect();
   private final Game game;
   float positionX = 5;
   float positionY = 15;
   ArrayList<Kirti> data = new ArrayList<Kirti>();
   String strgettile = null;
   
   Paint foreground = new Paint(Paint.ANTI_ALIAS_FLAG);
   String getorientation;
   
   String characterToString;
   Path path;
   List<Path> mTextPaths = new ArrayList<Path>();
   
   public PuzzleView(Context context) {
       super(context);
       this.game = (Game) context;
       setFocusable(true);
       setFocusableInTouchMode(true);
   }
   
   @Override
   protected void onSizeChanged(int w, int h, int oldw, int oldh) {
       width = w / 9f;
       height = h / 9f;
       // getRect(selX, selY, selRect);
       Log.d(TAG, "onSizeChanged: width " + width + ", height " + height);
       super.onSizeChanged(w, h, oldw, oldh);
   }
   
   @Override
   protected void onDraw(Canvas canvas) {
       // super.onDraw(canvas);
       // canvas.save();
       // canvas.restore();
       // Draw the background...
       Paint background = new Paint();
       background.setColor(getResources().getColor(R.color.puzzle_background));
       canvas.drawRect(0, 0, getWidth(), getHeight(), background);
   
       // Draw the board...
       // Define colors for the grid lines
       Paint dark = new Paint();
       dark.setColor(getResources().getColor(R.color.puzzle_dark));
   
       Paint hilite = new Paint();
       hilite.setColor(getResources().getColor(R.color.puzzle_hilite));
   
       Paint light = new Paint();
       light.setColor(getResources().getColor(R.color.puzzle_light));
   
       // Draw the minor grid lines
       for (int i = 0; i < 9; i++) {
           canvas.drawLine(0, i * height, getWidth(), i * height, light);
           canvas.drawLine(0, i * height + 1, getWidth(), i * height + 1,
                   hilite);
           canvas.drawLine(i * width, 0, i * width, getHeight(), light);
           canvas.drawLine(i * width + 1, 0, i * width + 1, getHeight(),
                   hilite);
       }
   
       // Draw the major grid lines
       for (int i = 0; i < 9; i++) {
           if (i % 3 != 0)
               continue;
           canvas.drawLine(0, i * height, getWidth(), i * height, dark);
           canvas.drawLine(0, i * height + 1, getWidth(), i * height + 1,
                   hilite);
           canvas.drawLine(i * width, 0, i * width, getHeight(), dark);
           canvas.drawLine(i * width + 1, 0, i * width + 1, getHeight(),
                   hilite);
       }
   
       Paint hint = new Paint();
       path = new Path();
   
       int m;
       for (int i = 0; i < data.size(); i++) {
           String strgettile = data.get(i).getSt();
   
           if (strgettile != null) {
               for (m = 0; m < strgettile.length(); m++) {
                   System.out.println(strgettile.charAt(m));
                   char convertst = strgettile.charAt(m);
                   characterToString = Character.toString(convertst);
   
                   if (data.get(i).getorientation
                           .equalsIgnoreCase("Horizontal")) {
   
                       canvas.drawText(characterToString, m
                               * data.get(i).getWidth()
                               + data.get(i).getXposition(), data.get(i)
                               .getYposition(), foreground); // for motion
                                                             // event
   
                       hint.setColor(Color.BLACK);
                       hint.setTextSize(45);
   
                   } else {
                       // mTextPaths.add(strgettile);
                       // for (int i = 0; i < mTextPaths.size(); i++) {
   
                       canvas.drawText(characterToString, data.get(i)
                               .getXposition(), m * data.get(i).getHeight()
                               + data.get(i).getYposition(), foreground);
                       // }
   
                       hint.setColor(Color.BLACK);
                       hint.setTextSize(45);
   
                   }
   
               }
               try {
                   if (foreground != null) {
                       foreground.getTextPath(characterToString, 0,
                               characterToString.length(), data.get(i)
                                       .getXposition() * 2 / 3, data.get(i)
                                       .getYposition() - 4, path);
                   }
   
               } catch (Exception e) {
   
               }
   
           }
       }
   
   }
   
   @Override
   public boolean onTouchEvent(MotionEvent event) {
       if (event.getAction() != MotionEvent.ACTION_DOWN)
           game.showKeypadOrError(selX, selY);
       foreground.setColor(getResources().getColor(R.color.puzzle_foreground));
       foreground.setStyle(Style.FILL);
       foreground.setTextSize(height * 0.75f);
       foreground.setTextScaleX(width / height);
       foreground.setTextAlign(Paint.Align.CENTER);
       FontMetrics fm = foreground.getFontMetrics();
       positionX = (int) event.getX();
       positionY = (int) event.getY() - (fm.ascent + fm.descent) / 2;
   
       return true;
   }
   
   public void setSelectedTile(String tile, String strorientations) {
       // TODO Auto-generated method stub
       Log.v("getting string in puzzle view ", tile);
       if (game.setTileIfValid(selX, selY, tile)) {
           strgettile = tile;
           getorientation = strorientations;
           mTextPaths.add(path);
           data.add(new Kirti(positionX, positionY, strgettile,
                   getorientation, width, height));
           invalidate();
           Log.v("getting mtextpaths", mTextPaths.toString());
       }
   
   }}
   

模型类是：

public class Kirti {
float positionX;
float positionY;
String strgettile;
String getorientation;
float width;
float height;
public Kirti(float positionX, float positionY, String strgettile,
        String getorientation, float width, float height) {
    super();
    this.positionX = positionX;
    this.positionY = positionY;
    this.strgettile = strgettile;
    this.getorientation = getorientation;
    this.width = width;
    this.height = height;
}
public float getPositionX() {
    return positionX;
}
public void setPositionX(float positionX) {
    this.positionX = positionX;
}
public float getPositionY() {
    return positionY;
}
public void setPositionY(float positionY) {
    this.positionY = positionY;
}
public String getStrgettile() {
    return strgettile;
}
public void setStrgettile(String strgettile) {
    this.strgettile = strgettile;
}
public String getGetorientation() {
    return getorientation;
}
public void setGetorientation(String getorientation) {
    this.getorientation = getorientation;
}
public float getWidth() {
    return width;
}
public void setWidth(float width) {
    this.width = width;
}
public float getHeight() {
    return height;
}
public void setHeight(float height) {
    this.height = height;
}}

Answer 2

我不会阅读那些包含所有无关事件处理的过长且格式可怕的代码......但一般来说，如果你想在两次绘制之间保存画布状态，你需要明确地做到这一点。

谷歌“屏幕绘图的机器人”

off screen drawing in android

在位图上绘制。 在画布上绘制该位图。 重复。