Question

import java.util.ArrayList;

import android.app.Activity;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Bundle;
import android.os.Handler;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup.LayoutParams;


    public class DrawingActivity extends Activity {
        private ArrayList _graphics = new ArrayList();
        private Paint mPaint;
        Handler myHandler = new Handler() {

        public void handleMessage(android.os.Message msg) {
        myview.invalidate();

        };
        };
        Myview myview;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // setContentView(new DrawingPanel(this));
        mPaint = new Paint();
        mPaint.setDither(true);
        mPaint.setColor(0xFFFFFF00);
        mPaint.setStyle(Paint.Style.STROKE);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeWidth(3);
        myview = new Myview(this);
        myview.setLayoutParams(new LayoutParams(LayoutParams.FILL_PARENT,
        LayoutParams.FILL_PARENT));
        setContentView(myview);
        myHandler = new Handler();

        }

        class Myview extends View {

        public Myview(Context context) {
        super(context);

        }

        Path path;

        @Override
        public boolean onTouchEvent(MotionEvent event) {
        if (event.getAction() == MotionEvent.ACTION_DOWN) {
        path = new Path();
        path.moveTo(event.getX(), event.getY());
        path.lineTo(event.getX(), event.getY());
        _graphics.add(path);
        } else if (event.getAction() == MotionEvent.ACTION_MOVE) {
        path.lineTo(event.getX(), event.getY());
        } else if (event.getAction() == MotionEvent.ACTION_UP) {
        path.lineTo(event.getX(), event.getY());
        }
        invalidate();
        return true;
        }

        @Override
        protected void onDraw(Canvas canvas) {
        for (Path path :_graphics) {
        // canvas.drawPoint(graphic.x, graphic.y, mPaint);
        canvas.drawPath(path, mPaint);
        }
        }
        }

        }

这里编译器显示该行中的错误类型不匹配：无法从元素类型Object转换为Path ---------- for（Path path：_graphics）{此处出现问题

Answer 1

您的ArrayList是无类型的，因此即使您可能只将那些类型的对象放在那里，编译器也不会知道它。您需要使用泛型（如果Android上的Java支持它），例如

ArrayList<Path> _graphics = new ArrayList<Path>();

或重写循环，以便您可以在从列表中获取元素时强制转换元素。

for (int c=0; c< _graphic.size(); ++c ) {
    Path p = (Path)_graphics.get(c);
    ....
}

祝你好运。

类型不匹配：无法从元素类型Object转换为Path for（Path path：_graphics）{

1 个答案: