Question

我想在屏幕上看到一个按钮和一个圆圈（用画布绘图）。但是我不能这样做，特别是在XML文件中看得很好但是当我将APK发送到我的手机时出现这个错误：

java.lang.RuntimeException：无法启动活动ComponentInfo {com.example.mehmet.catchtheball / com.example.mehmet.catchtheball.Customer}：android.view.InflateException：二进制XML文件行＃0：二进制XML文件第0行：输入类com.example.mehmet.catchtheball.MyView

时出错

我的activity_customer.xml显示屏幕截图： enter image description here

（很快，我也想在手机上显示这一点。）

MyView.java file:

package com.example.mehmet.catchtheball;

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

public class MyView extends View {

    public MyView(Context context) {
        super(context);
    }
    @Override
    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);
        Paint paint = new Paint();
        paint.setColor(Color.WHITE);
        canvas.drawPaint(paint);
        paint.setColor(Color.parseColor("lightGray"));
        canvas.drawCircle(500, 500, 150, paint);
    }
}

Customer.java档案：

package com.example.mehmet.catchtheball;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;


public class Customer extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_customer);
        MyView a = new MyView(this); //create a circle
        a.setOnTouchListener(new View.OnTouchListener() {
            public boolean onTouch(View view, MotionEvent motionEvent) {
               return true;
            }
        });
    }
}

activity_customer.xml档案：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativeLayout"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.mehmet.catchtheball.main">

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:text="@string/button" />

    <RelativeLayout
        android:id="@+id/relativeLayoutt"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentTop="true">

    </RelativeLayout>

    <com.example.mehmet.catchtheball.MyView
        android:id="@+id/view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true" />
</RelativeLayout>

Answer 1

您必须在MyView类中实现以下构造函数

public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);
}

public MyView(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
}

您的课程应如下所示： -

public class MyView extends View {

    public MyView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public MyView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

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


    @Override
    protected void onDraw(Canvas canvas) {

        super.onDraw(canvas);
        Paint paint = new Paint();
        paint.setColor(Color.WHITE);
        canvas.drawPaint(paint);
        paint.setColor(Color.parseColor("lightGray"));
        canvas.drawCircle(500, 500, 150, paint);
    }


}

如何结合两个视图？

1 个答案: