ClassCastException：无法将LinearLayout强制转换为（java类）

Question

尝试向活动添加滑出菜单后出现以下错误问题：

java.lang.ClassCastException: android.widget.LinearLayout cannot be cast to appname.SlideOutMenu

它发现错误的代码的特定部分是这样的：

public class MainActivity extends Activity implements View.OnClickListener {

SlideOutMenu root;

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.root = (SlideOutMenu) this.getLayoutInflater().inflate(R.layout.activity_main, null);
    this.setContentView(root);
}

这是我的xml文件的相关部分：

<LinearLayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 xmlns:tools="http://schemas.android.com/tools"
 xmlns:ads="http://schemas.android.com/apk/res-auto"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:paddingLeft="0dp"
 android:paddingRight="0dp"
 android:id="@+id/mainActivityLayout"
 android:paddingTop="0dp"
 android:paddingBottom="0dp"
 tools:context=".MainActivity"
 android:background="#ffffff"
 android:orientation="vertical">

<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/mainActivitySlideout"
    android:background="#2a80b9"
    android:orientation="vertical">

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/tempBtn1"
        android:onClick="toggleMenu"
        android:text="Button 1"/>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:onClick="toggleMenu"
        android:id="@+id/tempBtn2"
        android:text="Button 2"/>

    <Button
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/tempBtn3"
        android:onClick="toggleMenu"
        android:text="Button 3"/>
</LinearLayout>

这是我的SlideOutMenu类，如果需要的话：

package rule02.touchpool;

import android.content.Context;
import android.util.AttributeSet;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;

public class SlideOutMenu extends LinearLayout {
    private View menu;
    private View content;

    protected static final int menuMargin = 150;

    public enum MenuState {
        CLOSED, OPEN
    };

    protected int currentContentOffset = 0;
    protected MenuState menuCurrentState = MenuState.CLOSED;

    public SlideOutMenu(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    public SlideOutMenu(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

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

    protected void onAttachedToWindow() {
        super.onAttachedToWindow();

        this.menu = this.getChildAt(0);
        this.content = this.getChildAt(1);
        this.menu.setVisibility(View.GONE);
    }

    protected void onLayout(boolean changed, int left, int top, int right,
            int bottom) {
        if (changed) {
            this.calculateChildDimensions();
        }
        this.menu.layout(left, top, right - menuMargin, bottom);
        this.content.layout(left + this.currentContentOffset, top, right
                + this.currentContentOffset, bottom);
    }

    public void toggleMenu() {
        switch (this.menuCurrentState) {
        case CLOSED:
            this.menu.setVisibility(View.VISIBLE);
            this.currentContentOffset = this.getMenuWidth();
            this.content.offsetLeftAndRight(currentContentOffset);
            this.menuCurrentState = MenuState.OPEN;
            break;
        case OPEN:
            this.content.offsetLeftAndRight(-currentContentOffset);
            this.currentContentOffset = 0;
            this.menuCurrentState = MenuState.CLOSED;
            this.menu.setVisibility(View.GONE);
            break;
        }
        this.invalidate();
    }

    private int getMenuWidth() {
        return this.menu.getLayoutParams().width;
    }

    private void calculateChildDimensions() {
        this.content.getLayoutParams().height = this.getHeight();
        this.content.getLayoutParams().width = this.getWidth();
        this.menu.getLayoutParams().width = this.getWidth() - menuMargin;
        this.menu.getLayoutParams().height = this.getHeight();
    }
}

如果有人可以帮助我，我将非常高兴！ :)

编辑：

与在XML文档中将SlideOutMenu声明为根视图有关系吗？ 如果是这样，我不确定如何执行操作，也找不到任何相关信息。

Answer 1

间接连接的帖子 及其间接说明 ，现在遵循以下代码

SlideOutMenu root;
View container;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
container = getLayoutInflater().inflate(R.layout.activity_main, null);
root = (SlideOutMenu) container.findViewById(R.id.mainActivitySlideout);
 this.setContentView(container);
//the following codes can follow

您的xml

//the important part
<rule02.touchpool.SlideOutMenu 
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/mainActivitySlideout"
android:background="#2a80b9"
android:orientation="vertical">

其余的都还可以，请记住使用</rule02.touchpool.SlideOutMenu>将其关闭

Answer 2

我认为root是您的布局xml文件。 因此，用于修复编译错误的代码应为：

this.root = (LinearLayout) this.getLayoutInflater().inflate(R.layout.activity_main, null);

标准建议代码为：

setContentView(R.layout.activity_main);

注意：我更喜欢标准代码。

Answer 3

您可以使用XML或类来创建UI。 您如何同时使用两者并尝试将它们转换为另一种？ 它永远都行不通。 实例化布局Java类并在内容视图中对其进行设置，或者对xml进行膨胀并对其进行设置。

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    this.setContentView(this.getLayoutInflater().inflate(R.layout.activity_main, null));
}

或者你可以做

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    LinearLayout som = new SlideOutMenu(this);
    this.setContentView(som );
}