java - 尝试绘制自定义 View 时崩溃 - InflateException

Question

我尝试过寻找这个问题。我在其他问题中看到过类似的经历，但他们使用不同的资源。我试图在屏幕上绘制一个矩形，通过单击不同的按钮来执行不同的操作。我对 Android 还很陌生，所以任何帮助将不胜感激。我的预览看起来不错，与我想要做的一模一样，但在模拟器中崩溃了。

我正在尝试在我的 Activity 中绘制一个矩形。我创建了一个应该绘制三角形的自定义 View 类。然后，我尝试将该 View 添加到我的 content_main.xml 中，但它引发了 inflateException 错误。

ColorRectView 类:

public class ColorRectView extends View {

private Rect rectangle;
private Paint paint;

public ColorRectView(Context context) {
    super(context);
    int x = 50;
    int y = 50;
    int sideLength = 200;

    // Create a rectangle to hold the random color
    rectangle = new Rect(x, y, sideLength, sideLength);

    // Create the Paint and set it's color
    paint = new Paint();
    paint.setColor(Color.GRAY);
}

@Override
protected void onDraw(Canvas canvas) {
    canvas.drawRect(rectangle, paint);
}

content_main.xml

<android.support.constraint.ConstraintLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:layout_behavior="@string/appbar_scrolling_view_behavior"
tools:context=".MainActivity"
tools:showIn="@layout/activity_main">

<colorRectPractice.ColorRectView
    android:id="@+id/colorRectangle"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

// This was the original view container that I added using the design tab, gave me the same error
    <!--<view-->
    <!--class="colorRectPractice.ColorRectView"-->
    <!--id="@+id/view4"-->
    <!--android:layout_width="wrap_content"-->
    <!--android:layout_height="wrap_content"-->
    <!--tools:layout_editor_absoluteX="74dp"-->
    <!--tools:layout_editor_absoluteY="178dp" />-->


</android.support.constraint.ConstraintLayout>

我收到此错误:

java.lang.RuntimeException: Unable to start activity ComponentInfo{colorRectPractice/colorRectPractice.MainActivity}: android.view.InflateException: Binary XML file line #23: Binary XML file line #17: Error inflating class colorRectPractice.ColorRectView
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2817)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
    at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4754)
    at android.app.ActivityThread.-wrap18(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1599)
    at android.os.Handler.dispatchMessage(Handler.java:105)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6541)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)
 Caused by: android.view.InflateException: Binary XML file line #23: Binary XML file line #17: Error inflating class xyz.softdev.colorswipe.ColorRectView
 Caused by: android.view.InflateException: Binary XML file line #17: Error inflating class xyz.softdev.colorswipe.ColorRectView
 Caused by: java.lang.NoSuchMethodException: <init> [class android.content.Context, interface android.util.AttributeSet]
    at java.lang.Class.getConstructor0(Class.java:2320)
    at java.lang.Class.getConstructor(Class.java:1725)
    at android.view.LayoutInflater.createView(LayoutInflater.java:615)
    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:790)
    at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:730)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:863)
    at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
    at android.view.LayoutInflater.parseInclude(LayoutInflater.java:995)
    at android.view.LayoutInflater.rInflate(LayoutInflater.java:859)
    at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:824)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:515)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:423)
    at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
    at android.support.v7.app.AppCompatDelegateImplV9.setContentView(AppCompatDelegateImplV9.java:287)
    at android.support.v7.app.AppCompatActivity.setContentView(AppCompatActivity.java:139)
    at xyz.softdev.colorswipe.MainActivity.onCreate(MainActivity.java:22)
    at android.app.Activity.performCreate(Activity.java:6975)
    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1213)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2770)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2892)
    at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:4754)
    at android.app.ActivityThread.-wrap18(Unknown Source:0)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1599)
    at android.os.Handler.dispatchMessage(Handler.java:105)
    at android.os.Looper.loop(Looper.java:164)
    at android.app.ActivityThread.main(ActivityThread.java:6541)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.Zygote$MethodAndArgsCaller.run(Zygote.java:240)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:767)

Answer 1

您的自定义 View 构造函数中缺少AttributeSet。

这是制作简单饼图的示例。

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.BlurMaskFilter;
import android.graphics.Canvas;

import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RadialGradient;
import android.graphics.RectF;
import android.graphics.Shader.TileMode;
import android.util.AttributeSet;
import android.view.View;

import com.talview.recruit.R;

public class DonutChart extends View {

	
	 private float radius;
	
	 Paint paint;
	 Paint shadowPaint;
	 
	 Path myPath;
	 Path shadowPath;
	 
	 RectF outterCircle;
	 RectF innerCircle;
	 RectF shadowRectF;
	 
	public DonutChart(Context context, AttributeSet attrs) {
		super(context, attrs);
		
		TypedArray a = context.getTheme().obtainStyledAttributes(
                attrs,
                R.styleable.DonutChart,
                0, 0
        );
		
		try {
            radius = a.getDimension(R.styleable.DonutChart_radius, 20.0f);
        } finally {
            a.recycle();
        }
		
		paint = new Paint();
		paint.setDither(true);       
		paint.setStyle(Paint.Style.FILL); 
		paint.setStrokeJoin(Paint.Join.ROUND); 
		paint.setStrokeCap(Paint.Cap.ROUND);     
		paint.setAntiAlias(true); 
		paint.setStrokeWidth(radius / 14.0f);
		
		shadowPaint = new Paint();
	    shadowPaint.setColor(0xf0000000);
	    shadowPaint.setStyle(Paint.Style.STROKE); 
	    shadowPaint.setAntiAlias(true);
	    shadowPaint.setStrokeWidth(4.0f);
	    shadowPaint.setMaskFilter(new BlurMaskFilter(4, BlurMaskFilter.Blur.SOLID));


		myPath = new Path();
		shadowPath = new Path();


		outterCircle = new RectF();
		innerCircle = new RectF();
		shadowRectF = new RectF();

		float adjust = (.019f*radius);
		shadowRectF.set(adjust, adjust, radius*2-adjust, radius*2-adjust);
		
		adjust = .038f * radius;
		outterCircle.set(adjust, adjust, radius*2-adjust, radius*2-adjust);
		
		adjust = .276f * radius;
		innerCircle.set(adjust, adjust, radius*2-adjust, radius*2-adjust);

	}

	
	@Override
	protected void onDraw(Canvas canvas) {
		super.onDraw(canvas);


		
		// green	
		setGradient(0xff84BC3D,0xff5B8829); 
		drawDonut(canvas,paint, 0,60);		
		
		//red
		setGradient(0xffe04a2f,0xffB7161B); 
		drawDonut(canvas,paint, 60,60);
		
		// blue
		setGradient(0xff4AB6C1,0xff2182AD);
		drawDonut(canvas,paint, 120,60);
		
		// yellow
		setGradient(0xffFFFF00,0xfffed325);
		drawDonut(canvas,paint, 180,180);
	

		
	}
	
	public void drawDonut(Canvas canvas, Paint paint, float start,float sweep){

		myPath.reset();
		myPath.arcTo(outterCircle, start, sweep, false);
		myPath.arcTo(innerCircle, start+sweep, -sweep, false);
		myPath.close();
		canvas.drawPath(myPath, paint);
	}
	
	public void setGradient(int sColor, int eColor){
		paint.setShader(new RadialGradient(radius, radius, radius-5, 
				new int[]{sColor,eColor}, 
				new float[]{.6f,.95f},TileMode.CLAMP) );
	}
	
	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		
	    int desiredWidth = (int) radius*2;
	    int desiredHeight = (int) radius*2;

	    int widthMode = MeasureSpec.getMode(widthMeasureSpec);
	    int widthSize = MeasureSpec.getSize(widthMeasureSpec);
	    int heightMode = MeasureSpec.getMode(heightMeasureSpec);
	    int heightSize = MeasureSpec.getSize(heightMeasureSpec);

	    int width;
	    int height;

	    //70dp exact
	    if (widthMode == MeasureSpec.EXACTLY) {
	        width = widthSize;
	    }else if (widthMode == MeasureSpec.AT_MOST) {
		    //wrap content
	        width = Math.min(desiredWidth, widthSize);
	    } else {
	        width = desiredWidth;
	    }

	    //Measure Height
	    if (heightMode == MeasureSpec.EXACTLY) {
	        height = heightSize;
	    } else if (heightMode == MeasureSpec.AT_MOST) {
	        height = Math.min(desiredHeight, heightSize);
	    } else {
	        height = desiredHeight;
	    }

	    //MUST CALL THIS
	    setMeasuredDimension(width, height);
	}
	
	
}