将自定义视图添加到 Android Wear for canvas

Question

我正在尝试向 Round Android Wear 添加自定义视图，并从 logcat 收到以下错误：

12-31 19:27:27.211 2212-2212/? E/AndroidRuntime: FATAL EXCEPTION: main
                                                 Process: com.example.crashoveride007.roundwatchcanvas, PID: 2212
                                                 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.crashoveride007.roundwatchcanvas/com.example.crashoveride007.roundwatchcanvas.MainActivity}: android.view.InflateException: Binary XML file line #10: Error inflating class com.example.crashoveride007.roundwatchcanvas.MyView
                                                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
                                                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387)
                                                     at android.app.ActivityThread.access$800(ActivityThread.java:151)
                                                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
                                                     at android.os.Handler.dispatchMessage(Handler.java:102)
                                                     at android.os.Looper.loop(Looper.java:135)
                                                     at android.app.ActivityThread.main(ActivityThread.java:5254)
                                                     at java.lang.reflect.Method.invoke(Native Method)
                                                     at java.lang.reflect.Method.invoke(Method.java:372)
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
                                                  Caused by: android.view.InflateException: Binary XML file line #10: Error inflating class com.example.crashoveride007.roundwatchcanvas.MyView
                                                     at android.view.LayoutInflater.createView(LayoutInflater.java:616)
                                                     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:743)
                                                     at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
                                                     at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
                                                     at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
                                                     at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
                                                     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:378)
                                                     at android.app.Activity.setContentView(Activity.java:2145)
                                                     at com.example.crashoveride007.roundwatchcanvas.MainActivity.onCreate(MainActivity.java:16)
                                                     at android.app.Activity.performCreate(Activity.java:5990)
                                                     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
                                                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
                                                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
                                                     at android.app.ActivityThread.access$800(ActivityThread.java:151) 
                                                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
                                                     at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                     at android.os.Looper.loop(Looper.java:135) 
                                                     at android.app.ActivityThread.main(ActivityThread.java:5254) 
                                                     at java.lang.reflect.Method.invoke(Native Method) 
                                                     at java.lang.reflect.Method.invoke(Method.java:372) 
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
                                                  Caused by: java.lang.NoSuchMethodException: <init> [class android.content.Context, interface android.util.AttributeSet]
                                                     at java.lang.Class.getConstructor(Class.java:531)
                                                     at java.lang.Class.getConstructor(Class.java:495)
                                                     at android.view.LayoutInflater.createView(LayoutInflater.java:580)
                                                     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:743) 
                                                     at android.view.LayoutInflater.rInflate(LayoutInflater.java:806) 
                                                     at android.view.LayoutInflater.inflate(LayoutInflater.java:504) 
                                                     at android.view.LayoutInflater.inflate(LayoutInflater.java:414) 
                                                     at android.view.LayoutInflater.inflate(LayoutInflater.java:365) 
                                                     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:378) 
                                                     at android.app.Activity.setContentView(Activity.java:2145) 
                                                     at com.example.crashoveride007.roundwatchcanvas.MainActivity.onCreate(MainActivity.java:16) 
                                                     at android.app.Activity.performCreate(Activity.java:5990) 
                                                     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106) 
                                                     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278) 
                                                     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2387) 
                                                     at android.app.ActivityThread.access$800(ActivityThread.java:151) 
                                                     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303) 
                                                     at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                     at android.os.Looper.loop(Looper.java:135) 
                                                     at android.app.ActivityThread.main(ActivityThread.java:5254) 
                                                     at java.lang.reflect.Method.invoke(Native Method) 
                                                     at java.lang.reflect.Method.invoke(Method.java:372) 
                                                     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
                                                     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 

这是 MyView 自定义视图类：

package com.example.crashoveride007.roundwatchcanvas;

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

/**
 * Created by Crash.Overide.007 on 2/24/16.
 */
public class MyView extends View{

    Paint myPaint;
    Bitmap image;

    public MyView(Context context) {
        super(context);
        image = BitmapFactory.decodeResource(getResources(),R.drawable.ok);
        myPaint = new Paint();
        myPaint.setColor(Color.WHITE);
        myPaint.setStrokeWidth(10);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawBitmap(image,137,0,null);
    }
}

MainActivity 类：

package com.example.crashoveride007.roundwatchcanvas;

import android.app.Activity;
import android.os.Bundle;
import android.support.wearable.view.WatchViewStub;
import android.widget.RelativeLayout;
import android.widget.TextView;

public class MainActivity extends Activity {

    private TextView mTextView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.round_activity_main);
        final RelativeLayout main = (RelativeLayout) findViewById(R.id.roundWatch);
    }
}

round_activity_main 的 XML：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/roundWatch"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.crashoveride007.roundwatchcanvas.MainActivity"
    tools:deviceIds="wear_round">

    <com.example.crashoveride007.roundwatchcanvas.MyView
        android:id="@+id/myView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
</RelativeLayout>

谁能帮助我消除此错误并了解如何在穿着活动中使用画布？

谢谢。

Answer 1

您需要为视图提供额外的构造函数才能正确膨胀。至少，您需要一个将Context 和AttributeSet 作为参数的参数，如下所示：

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

根据View 文档，这种“第二种形式应该解析并应用布局文件中定义的任何属性。”

您通常也应该覆盖其他两个标准的View 构造函数： http://developer.android.com/reference/android/view/View.html#pubctors