java - 将自定义 View 添加到 xml 布局

Question

我有这个签名 View ，基本上可以让您在手机屏幕上绘图。现在我需要将此 View 添加为背景或将其用作 xml 布局上的小部件，但我不知道该怎么做。所以请任何人都可以帮助我做到这一点。 这是我拥有的签名 View 类:

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class SignatureView extends View {

      private static final float STROKE_WIDTH = 5f;

      /** Need to track this so the dirty region can accommodate the stroke. **/
      private static final float HALF_STROKE_WIDTH = STROKE_WIDTH / 2;

      private Paint paint = new Paint();
      private Path path = new Path();

      /**
       * Optimizes painting by invalidating the smallest possible area.
       */
      private float lastTouchX;
      private float lastTouchY;
      private final RectF dirtyRect = new RectF();

      public SignatureView(Context context, AttributeSet attrs, int background) {
        super(context, attrs);
        setBackgroundResource(background);
        paint.setAntiAlias(true);
        paint.setColor(Color.BLACK);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);
        paint.setStrokeWidth(STROKE_WIDTH);

      }

      public void setColor(int color){
          paint.setColor(color);
      }

      /**
       * Erases the signature.
       */
      public void clear() {
        path.reset();

        // Repaints the entire view.
        invalidate();
      }

      @Override
      protected void onDraw(Canvas canvas) {
        canvas.drawPath(path, paint);
      }

      @Override
      public boolean onTouchEvent(MotionEvent event) {
        float eventX = event.getX();
        float eventY = event.getY();

        switch (event.getAction()) {
          case MotionEvent.ACTION_DOWN:
            path.moveTo(eventX, eventY);
            lastTouchX = eventX;
            lastTouchY = eventY;
            // There is no end point yet, so don't waste cycles invalidating.
            return true;

          case MotionEvent.ACTION_MOVE:
          case MotionEvent.ACTION_UP:
            // Start tracking the dirty region.
            resetDirtyRect(eventX, eventY);

            // When the hardware tracks events faster than they are delivered, the
            // event will contain a history of those skipped points.
            int historySize = event.getHistorySize();
            for (int i = 0; i < historySize; i++) {
              float historicalX = event.getHistoricalX(i);
              float historicalY = event.getHistoricalY(i);
              expandDirtyRect(historicalX, historicalY);
              path.lineTo(historicalX, historicalY);
            }

            // After replaying history, connect the line to the touch point.
            path.lineTo(eventX, eventY);
            break;

          default:
//          Log.("Ignored touch event: " + event.toString());
            return false;
        }

        // Include half the stroke width to avoid clipping.
        invalidate(
            (int) (dirtyRect.left - HALF_STROKE_WIDTH),
            (int) (dirtyRect.top - HALF_STROKE_WIDTH),
            (int) (dirtyRect.right + HALF_STROKE_WIDTH),
            (int) (dirtyRect.bottom + HALF_STROKE_WIDTH));

        lastTouchX = eventX;
        lastTouchY = eventY;

        return true;
      }

      /**
       * Called when replaying history to ensure the dirty region includes all
       * points.
       */
      private void expandDirtyRect(float historicalX, float historicalY) {
        if (historicalX < dirtyRect.left) {
          dirtyRect.left = historicalX;
        } else if (historicalX > dirtyRect.right) {
          dirtyRect.right = historicalX;
        }
        if (historicalY < dirtyRect.top) {
          dirtyRect.top = historicalY;
        } else if (historicalY > dirtyRect.bottom) {
          dirtyRect.bottom = historicalY;
        }
      }

      /**
       * Resets the dirty region when the motion event occurs.
       */
      private void resetDirtyRect(float eventX, float eventY) {

        // The lastTouchX and lastTouchY were set when the ACTION_DOWN
        // motion event occurred.
        dirtyRect.left = Math.min(lastTouchX, eventX);
        dirtyRect.right = Math.max(lastTouchX, eventX);
        dirtyRect.top = Math.min(lastTouchY, eventY);
        dirtyRect.bottom = Math.max(lastTouchY, eventY);
      }
    }

和我的主要类(class):

public class Draw extends Activity {
    DrawView drawView;
    SignatureView signature;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Set full screen view
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        requestWindowFeature(Window.FEATURE_NO_TITLE);

        signature = new SignatureView(this, null,R.drawable.back);

        setContentView(signature);
        signature.requestFocus();
    }

    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.my_options_menu, menu);
        return true;
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case R.id.clear:
            signature.clear();
            return true;

        case R.id.red:
            signature.setColor(Color.RED);
            return true;

        case R.id.blue:
            signature.setColor(Color.BLUE);
            return true;
        case R.id.yellow:
            signature.setColor(Color.YELLOW);
            return true;
        default:
            return super.onOptionsItemSelected(item);
        }
    }

    @Override
    public void onBackPressed() {
        this.finish();
        super.onBackPressed();
    }
}

Answer 1

您将在 XML 布局中通过全名引用它，例如 com.example.myapp.SignatureView。

<com.example.myapp.SignatureView android:id="@+id\my_id"
      android:layout_width="match_parent"
      android:layout_height="match_parent">
</com.example.myapp.SignatureView>

你也可以在后面的代码中正常引用它

SignatureView sv = (SignatureView)findViewById(R.id.my_id);
sv.setColor(Color.RED);