如何让按钮在android中使用视图[关闭]

Question

我一直在尝试向这个绘图应用程序添加擦除功能。我本来打算在你移动手指的地方简单地画白色。出于某种原因，我无法让按钮工作。如果我能让这个按钮工作，我将能够添加更多颜色等。 （我没有对 Mainactivity 做过任何事情）

package com.example.draw;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Bundle;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainDrawingView extends View
{
private Paint paint = new Paint();
private boolean erase;
private Path path = new Path();
Button aButton;

public MainDrawingView(Context context, AttributeSet attrs)
{
    super(context, attrs);
    paint.setAntiAlias(true);
    paint.setStrokeWidth(5f);
    paint.setStyle(Paint.Style.STROKE);
    paint.setStrokeJoin(Paint.Join.ROUND);

    aButton = (Button) this.findViewById(R.id.button1);
    aButton.setOnClickListener(new OnClickListener()
    {
        public void onClick(View v)
        {
            erase = !erase;
        }
    });
}

@Override
protected void onDraw(Canvas canvas)
{
    canvas.drawPath(path, paint);
}

public boolean onTouchEvent(MotionEvent event)
{
    if(erase) paint.setColor(Color.WHITE);
    else paint.setColor(Color.BLACK);

    // Get the coordinates of the touch event.
    float eventX = event.getX();
    float eventY = event.getY();
    switch (event.getAction()) {
        case MotionEvent.ACTION_DOWN:
            // Set a new starting point
            path.moveTo(eventX, eventY);
            return true;
        case MotionEvent.ACTION_MOVE:
            // Connect the points
            path.lineTo(eventX, eventY);
            break;
        default:
            return false;
    }

    // Makes our view repaint and call onDraw

    invalidate();

    return true;
}
}
Activity_main<

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:background="#ffffff"

tools:context="com.example.draw.FullscreenActivity">



<!-- This is the view on which we will draw. -->

<view

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    class="com.example.draw.MainDrawingView"
    android:id="@+id/single_touch_view"

    android:layout_gravity="left|top"
    android:background="#ffffff" />

<Button
    android:id="@+id/button1"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Button" />

</FrameLayout>

Answer 1

您的问题似乎是您使用了错误的类型。您的 erase 变量的类型为 Paint：

private Paint erase = new Paint();

但在您的代码中，您将其视为代表boolean 的int。

if(erase != 0) { paint.setColor(Color.BLACK); }
if(erase == 0) { paint.setColor(Color.WHITE); }
...
erase = 1;

其次，你从来没有真正为你的按钮设置onClickListener。此外，设置颜色的逻辑应该全部移到您的onTouch 或onClick 方法中。你真的应该有：

public class MainDrawingView extends View
{
    private Paint paint = new Paint();
    private boolean erase;
    private Path path = new Path();
    Button aButton;

    public MainDrawingView(Context context, AttributeSet attrs)
    {
        super(context, attrs);
        paint.setAntiAlias(true);
        paint.setStrokeWidth(5f);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeJoin(Paint.Join.ROUND);

        aButton = (Button) this.findViewById(R.id.button1);
        aButton.setOnClickListener(new OnClickListener()
        {
            public void onClick(View v)
            {
                erase = !erase;
            }
        });
    }

    @Override
    protected void onDraw(Canvas canvas)
    {
        canvas.drawPath(path, paint);
    }

    public boolean onTouchEvent(MotionEvent event)
    {
        if(erase) paint.setColor(Color.WHITE);
        else paint.setColor(Color.BLACK);

        // Get the coordinates of the touch event.
        float eventX = event.getX();
        float eventY = event.getY();
        switch (event.getAction()) {
            case MotionEvent.ACTION_DOWN:
                // Set a new starting point
                path.moveTo(eventX, eventY);
                return true;
            case MotionEvent.ACTION_MOVE:
                // Connect the points
                path.lineTo(eventX, eventY);
                break;
            default:
                return false;
        }

        // Makes our view repaint and call onDraw

        invalidate();

        return true;
    }
}

Answer 2

您的视图可能不是使用以下构造函数创建的

Context context, AttributeSet attrs

它可能正在使用您尚未覆盖的不同默认构造函数。然后什么都不会设置，你也不会得到任何你期望从你的听众那里得到的点击行为。

Answer 3

您似乎没有设置 onCreate(Bundle savedInstances) 方法来正确添加侦听器。