Question

此应用程序基本上可以让您从色轮中选择颜色并允许您更改应用程序的背景页面颜色，但是，每当我尝试从色轮向外部滑动时，该应用程序由于某种原因而崩溃。以下是我的MainActivity.java文件代码

 package com.example.colorpicker_assignment2;

import android.annotation.SuppressLint;
import android.graphics.Bitmap;
import android.graphics.Color;

import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.appcompat.app.AppCompatActivity;
import androidx.constraintlayout.widget.ConstraintLayout;


public class MainActivity extends AppCompatActivity  {


        Bitmap map; //represent the color wheel on a circular grid composed of individual dots corresponding to our pixels
    @SuppressLint("ClickableViewAccessibility")
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
  final ImageView color_wheel = findViewById(R.id.color_wheel); //find the color wheel
        final TextView color_results = findViewById(R.id.color_results); //find the text to print the color

    color_wheel.setDrawingCacheEnabled(true);
    color_wheel.buildDrawingCache(true);


        final ConstraintLayout layout = findViewById(R.id.constlayout); //define a contraint layout object to set the background color
//An interface to handle a touch event
        color_wheel.setOnTouchListener(new View.OnTouchListener(){
            @Override

            public boolean onTouch(View v, MotionEvent event)
            {
                if(event.getAction()==MotionEvent.ACTION_DOWN||event.getAction()==MotionEvent.ACTION_MOVE)
                {
                   map = color_wheel.getDrawingCache();
                    int pixel = map.getPixel((int)event.getX(),(int)event.getY());
                   //get the RGB values
                    int Red = Color.red(pixel); //assign the red pixel values collected to variable R
                    int Green = Color.green(pixel);//assign the green pixels collected to va
                    int Blue = Color.blue(pixel);

                    //get the hex values
                    String hexadecimal = "#"+Integer.toHexString(pixel);

                    //set background color
                    layout.setBackgroundColor(Color.rgb(Red,Green,Blue));

                    color_results.setText("RGB: "+Red+" ,"+Green+" ,"+Blue+"\nHEX: "+hexadecimal);
                }
                return true;
            }

        });
    }
}

以下是我的activity_main.xml文件：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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:id="@+id/constlayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <!--Pick a color from this image -->

    <ImageView
        android:id="@+id/color_wheel"
        android:layout_width="352dp"
        android:layout_height="309dp"
        android:layout_marginTop="60dp"
        android:clickable="true"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:srcCompat="@drawable/wheel" />

    <TextView
        android:id="@+id/color_results"
        android:layout_width="249dp"
        android:layout_height="103dp"
        android:layout_marginTop="16dp"
        android:text="Hex: \nRGB:"
        android:textColor="#000"
        android:textSize="18sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.24"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:text="@string/Backgroundcolorvalues"
        android:textSize="18sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/color_wheel" />

    <TextView
        android:id="@+id/title"
        android:layout_width="320dp"
        android:layout_height="58dp"
        android:layout_marginTop="4dp"
        android:text="@string/title"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.59"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constraintlayout.widget.ConstraintLayout>

这是我收到的错误消息：

E/InputEventReceiver: Exception dispatching input event.
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.colorpicker_assignment2, PID: 24845
    java.lang.IllegalArgumentException: y must be < bitmap.height()
        at android.graphics.Bitmap.checkPixelAccess(Bitmap.java:1958)
        at android.graphics.Bitmap.getPixel(Bitmap.java:1863)
        at com.example.colorpicker_assignment2.MainActivity$1.onTouch(MainActivity.java:43)
        at android.view.View.dispatchTouchEvent(View.java:13411)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3060)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2755)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3060)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2755)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3060)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2755)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3060)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2755)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3060)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2755)
        at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:3060)
        at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2755)
        at com.android.internal.policy.DecorView.superDispatchTouchEvent(DecorView.java:465)
        at com.android.internal.policy.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1849)
        at android.app.Activity.dispatchTouchEvent(Activity.java:3993)
        at androidx.appcompat.view.WindowCallbackWrapper.dispatchTouchEvent(WindowCallbackWrapper.java:69)
        at com.android.internal.policy.DecorView.dispatchTouchEvent(DecorView.java:423)
        at android.view.View.dispatchPointerEvent(View.java:13674)
        at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:5482)
        at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:5285)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4788)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4841)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4807)
        at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:4947)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4815)
        at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:5004)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4788)
        at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:4841)
        at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:4807)
        at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:4815)
        at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:4788)
        at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:7505)
        at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:7474)
        at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:7435)
        at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:7630)
        at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:188)
        at android.view.InputEventReceiver.nativeConsumeBatchedInputEvents(Native Method)
        at android.view.InputEventReceiver.consumeBatchedInputEvents(InputEventReceiver.java:178)
        at android.view.ViewRootImpl.doConsumeBatchedInput(ViewRootImpl.java:7581)
        at android.view.ViewRootImpl$ConsumeBatchedInputRunnable.run(ViewRootImpl.java:7654)
        at android.view.Choreographer$CallbackRecord.run(Choreographer.java:966)
        at android.view.Choreographer.doCallbacks(Choreographer.java:790)
        at android.view.Choreographer.doFrame(Choreographer.java:718)
        at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:951)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7356)
E/AndroidRuntime:     at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
I/Process: Sending signal. PID: 24845 SIG: 9
Disconnected from the target VM, address: 'localhost:8605', transport: 'socket'

这是我的色轮的图像：

Answer 1

线索在LogCat中：

java.lang.IllegalArgumentException: y must be < bitmap.height()

滑动时，event X和Y可能会超出范围。

因此，一个简单的解决方法是忽略太大的X和Y：

map = color_wheel.getDrawingCache();
// Add this
if (event.getX() >= map.getWidth() || event.getY() >= map.getHeight())
    return true;
// To here
int pixel = map.getPixel((int)event.getX(),(int)event.getY());

每当我在色轮外滑动时，我的应用就会崩溃

1 个答案: