android - 如何更新 Canvas 绘制文本而不是重绘 Canvas

Question

我现在可以在运动 View 的 Canvas 上绘制文本，问题是当我绘制文本并在同一 Canvas 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，因为我想要无效保留我以前的绘图并在同一 Canvas 上绘制新绘图我要怎么做？

@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。所以我维护所有的文本和位置 在 arraylist 中，并在每次单击 Canvas 时绘制 Canvas 。

2. 这是解决您问题的方法之一。 Canvas 只是一个 位图。无论你在上面画什么，它都是永久的。有办法 处理它，但大多数实现只是重新绘制整个 Canvas 在每一遍上。

   下面是代码 fragment :

   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());
       }
   
   }}
   

The model class is:

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;
}}