Question

我正在写一位Android画家。

这是我的主要内容：

package com.example.hwpainterandfilemanager;

import android.os.Bundle;
import android.app.Activity;
import android.graphics.Color;
import android.view.Menu;
import android.view.MenuItem;

public class MainPainter extends Activity {
    MyPainter painter ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        painter = new MyPainter(getApplicationContext());
        setContentView(R.layout.activity_main_painter);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main_painter, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // TODO Auto-generated method stub
        switch (item.getItemId()){

            case (R.id.Blue ):{ 
                painter.mColor = Color.BLUE;
                break;
            }

            case (R.id.Red ):{  
                painter.mColor=Color.RED;
                break;
            }
            case (R.id.Yellow ):{   
                painter.mColor = Color.YELLOW;
                break;
            }
            case (R.id.Green ):{    
                painter.mColor = Color.GREEN;
                break;
            } 

        }
        return super.onOptionsItemSelected(item);
    }
}

这是MyPanter：

package com.example.hwpainterandfilemanager;

import java.util.Vector;

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


public class MyPainter extends View {



    Vector<MyDot> allDots;
    int mColor;
    Paint p ;

    public MyPainter(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        // TODO Auto-generated constructor stub
        init();

    }


    public MyPainter(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        init();
    }

    public MyPainter(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        init();
    }

    public void init(){
        allDots = new Vector <MyDot> ();

        mColor = Color.BLUE;
    }


    @Override
    protected void onDraw(Canvas canvas) {
        // TODO Auto-generated method stub
        super.onDraw(canvas);

         p= new Paint();
         p.setStrokeWidth(5);

            for (int i =0 ; i<allDots.size();i++){
                p.setColor(allDots.get(i).mColor);
                canvas.drawPoint(allDots.get(i).mX, allDots.get(i).mY, p);
            }

    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        int x,y;

        if(MotionEvent.ACTION_DOWN==event.getAction() || MotionEvent.ACTION_MOVE==event.getAction()){
            x= (int) event.getX();
            y= (int) event.getY();
            MyDot tmp;
            tmp = new MyDot(x, y, mColor);

            Log.i("Painter Color", "" + mColor);
            allDots.add(tmp);

            invalidate();

            }


        // TODO Auto-generated method stub
        return true;
    }

}

和MyDot类：

package com.example.hwpainterandfilemanager;

public class MyDot {


        int mX =0;
        int mY =0;
        int mColor;

        public MyDot (int x, int y, int color) {
            mX=x;
            mY=y;
            mColor = color;
        }
    }

当尝试将颜色从蓝色更改为任何其他颜色时，颜色不会改变并保持不变。

我发现它工作的唯一方法是将mColor设置为静态，但这不是我想解决这个问题的方式。

我错过了什么？

THX，阿夫纳。

Answer 1

您正在创建两个Painter类实例，并且您正在更新错误的实例。问题出在MyPainter活动中。改变这个：

    painter = new MyPainter(getApplicationContext());
    setContentView(R.layout.activity_main_painter);

进入这个：

    painter = new MyPainter(getApplicationContext());
    setContentView(painter);

试图通过菜单改变颜色

1 个答案: