Question

我创建了一个类：

public class TestCanvas extends View {

    public TestCanvas(Context context) {
        super(context);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint = new Paint();
        paint.setColor(Color.RED);

        canvas.drawText("kal", 0, 100, paint);
        canvas.save();
    }
}

现在我从活动中调用该类：

public class TestActivity extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        TestCanvas tcanvas=new TestCanvas();

        frameLayout=(FrameLayout)findViewById(R.id.frameLayout1);
        frameLayout.addView(tcanvas);   
    }
}

现在我想将canvas插入活动类并设置为ImageView。我该怎么做？

Answer 1

您需要从View继承自己的班级并覆盖onDraw()和onMeasure()。就像你开始使用TestCanvas一样。一个例子：

package com.yourapphere;

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

public class TwoDee extends View {
    private int mWidth;
    private int mHeight;


    public TwoDee(Context context) {
        super(context);
    }

    public TwoDee(Context context, AttributeSet attribs) {
        super(context, attribs);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint = new Paint(); 
        paint.setColor(Color.GRAY); 
        paint.setStyle(Style.FILL); 
        canvas.drawPaint(paint);

        paint.setColor(Color.BLUE);
        canvas.drawLine(0, 0, mWidth, mHeight, paint);
        canvas.drawLine(mWidth, 0, 0, mHeight, paint);

        paint.setColor(Color.RED);
        canvas.drawText("0 kal", 50, 85, paint);
        canvas.save();
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        mWidth = View.MeasureSpec.getSize(widthMeasureSpec);
        mHeight = View.MeasureSpec.getSize(heightMeasureSpec);
        setMeasuredDimension(mWidth, mHeight);
    }
}

将自定义视图添加到活动的xml布局中，如下所示。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
        <TextView  
            android:layout_width="fill_parent" 
            android:layout_height="wrap_content" 
            android:text="@string/hello"
        />
        <com.yourapphere.TwoDee
            android:layout_width="150dp"
            android:layout_height="100dp"
        />
</LinearLayout>

您的活动课程没有任何内容。就是这样！

如果您确实需要使用ImageView：从ImageView而不是View继承您的自定义视图。然后使用自定义ImageView（如com.yourapphere.MyImageView）替换活动布局xml中的相应ImageView标记

参考文献＆amp;链接
请参阅类似问题：How to take canvas on imageview in android
简单的自定义视图示例代码：Adding my custom View into an XML layout throws exception

了解Android 2D绘图：http://developer.android.com/guide/topics/graphics/2d-graphics.html
Android 2D编码教程：http://www3.ntu.edu.sg/home/ehchua/programming/android/Android_2D.html
简单的2D游戏教程：http://www.barebonescoder.com/2010/06/android-development-simple-2d-graphics-part-1/

Answer 2

以下是针对具有相同问题的人士的解决方案

public class TestActivity extends Activity {

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    TestCanvas tcanvas=new TestCanvas();

    frameLayout=(FrameLayout)findViewById(R.id.frameLayout1);
    frameLayout.addView(tcanvas);

    Bitmap bitmap=Bitmap.createBitmap(440,587,Bitmap.Config.ARGB_8888);
    Canvas c=new Canvas(bitmap);
    tcanvas.draw(bitmap);

    //now i use bitmap at for any use.......

  }
}

如何使用视图扩展类的canvas进入活动类？

2 个答案: