java - Android:找不到这个imageView？

Question

我正在从输入流加载位图并将其放在 ImageView 上。然后我有一个按钮应该在位图上绘制一个圆圈。错误是在 onClickListener 中找不到 imageview(称为“touch”)...我该如何解决这个问题？当我按下按钮时什么也没有发生。 (注:ZoomInZoomOut类是Imageview的扩展)

    try {
        java.io.FileInputStream in = this.openFileInput(path);
        Bitmap bitmap = BitmapFactory.decodeStream(in);
        ZoomInZoomOut touch = (ZoomInZoomOut)findViewById(R.id.IMAGEID);
        touch = arrangeImageView(touch);
        touch.setImageBitmap(bitmap);
        in.close();
        Button draw = (Button) findViewById(R.id.draw);
        draw.setOnClickListener(new View.OnClickListener(){
            public void onClick(View v)
            {
                Bitmap imageBitmap = Bitmap.createBitmap(200,
                    200, Bitmap.Config.ARGB_8888);
                Canvas canvas = new Canvas(imageBitmap);
                Paint p = new Paint();
                p.setAntiAlias(true);
                p.setColor(Color.BLUE);
                canvas.drawCircle(60, 50, 25, p);
             /////////////////////Error is on the next line:
                touch.setImageBitmap(imageBitmap);
            }
        });

    } catch (Exception e) {
        e.printStackTrace();
    }

这是 XML:

<RelativeLayout 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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
android:background="@drawable/background"
tools:context="com.commonsware.android.test1.ImageDisplayActivity"
>


<com.commonsware.android.test1.ZoomInZoomOut
    android:id="@+id/IMAGEID"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_alignParentTop="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true"/>

<Button
    style="?android:attr/buttonStyleSmall"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="o"
    android:id="@+id/draw"
    android:layout_alignParentBottom="true"
    android:layout_alignParentLeft="true"
    android:layout_alignParentStart="true" />


</RelativeLayout>

Answer 1

touch 变量是在另一个作用域中定义的。如果您想了解更多说明，请查看此 link .

要解决您的问题，请更改您的代码，如下所示:

final ZoomInZoomOut touch = (ZoomInZoomOut)findViewById(R.id.IMAGEID);

或者如果您稍后需要从另一个作用域访问它，您也可以在类中创建一个变量:

private ZoomInZoomOut touch;

并像这样实例化:

touch = (ZoomInZoomOut)findViewById(R.id.IMAGEID);