layout.xml中的自定义RelativeLayouts

Question

我有一个自定义RelativeLayout remote_image_view.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content">
    <ImageView
            android:id="@+id/image"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/placeholder"
        />
</RelativeLayout>

好的,现在我想把它包含在main.xml:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:orientation="vertical" android:layout_width="fill_parent"
              android:layout_height="fill_parent">
    <Button android:text="Start Download" android:id="@+id/button1"
            android:layout_width="wrap_content" android:layout_height="wrap_content"
            android:onClick="onClick" />
    <Button android:text="View Downloads" android:id="@+id/button2"
            android:layout_width="wrap_content" android:layout_height="wrap_content"
            android:onClick="showDownload" />
    <ScrollView
        android:layout_height="fill_parent"
        android:layout_width="fill_parent"
        >
        <LinearLayout
                android:id="@+id/lay"
                android:layout_height="wrap_content"
                android:layout_width="wrap_content"
                android:orientation="vertical"
                >
            <include layout="@layout/remote_image_view" android:id="@+id/imageView1" />
            <include layout="@layout/remote_image_view" android:id="@+id/imageView2"/>
            <include layout="@layout/remote_image_view" android:id="@+id/imageView3"/>
            <include layout="@layout/remote_image_view" android:id="@+id/imageView4"/>
            <include layout="@layout/remote_image_view" android:id="@+id/imageView5"/>
            <include layout="@layout/remote_image_view" android:id="@+id/imageView6"/>
        </LinearLayout>
    </ScrollView>
</LinearLayout>

非常好.所以我创建了一个类RemoteImage:

public class RemoteImageView extends RelativeLayout {

    public RemoteImageView(Context context) {
        super(context);
    }

    public void init(RelativeLayout.LayoutParams layoutParams) {
        LayoutInflater inflater = (LayoutInflater)getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        inflater.inflate(R.layout.remote_image_view, this);
        setLayoutParams(layoutParams);
    }
}

并且出现了一个疯狂的问题.我不能编写如下代码:

RemoteImageView rm1 = (RemoteImageView)findViewById(R.id.imageView1);

因为我会得到例外:

java.lang.ClassCastException: android.widget.RelativeLayout cannot be cast to com.dmact.remoteimage.RemoteImageView

所以我应该RemoteImageView动态创建一个实例,然后应用一些LayoutParams.有没有办法不这样做？我想用XML编写布局,而不是代码.

Answer 1

如果需要使用RemoteImageView类继承RelativeLayout,则还必须在XML文件中指定类

前

<?xml version="1.0" encoding="utf-8"?>
<com.yourpackagepath.RemoteImageView
              xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content">
    <ImageView
            android:id="@+id/image"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/placeholder"
        />
</com.yourpackagepath.RemoteImageView>