Android：LayoutParams中addRule上的ArrayIndexOutOfBounds异常

Question

我写了这个函数：

private void SetNewsBackButton(Boolean visible)
{
    LinearLayout backButton = (LinearLayout)findViewById(R.id.backButton);
    TextView headerText = (TextView)findViewById(R.id.headerText);
    RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)headerText.getLayoutParams();
    if (visible)
    {
        backButton.setVisibility(View.VISIBLE);
        params.addRule(RelativeLayout.END_OF, R.id.backButton);
    } else {
        backButton.setVisibility(View.INVISIBLE);
        params.addRule(RelativeLayout.END_OF, 0);
    }
}

该函数应使LinearLayout可见或不可见，并在可见时将文本字段与其对齐，在不可见时不对齐。

我的问题：应用程序崩溃了

09-10 12:48:32.260  16663-16663/nidhoegger.org.nfansde W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0x41a9c600)
09-10 12:48:32.270  16663-16663/nidhoegger.org.nfansde E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.ArrayIndexOutOfBoundsException: length=16; index=19
        at android.widget.RelativeLayout$LayoutParams.addRule(RelativeLayout.java:1222)
        at nidhoegger.org.nfansde.NewsList.SetNewsBackButton(NewsList.java:147)
        at nidhoegger.org.nfansde.NewsList.ReadNews(NewsList.java:182)
        at nidhoegger.org.nfansde.NewsList$1.onItemClick(NewsList.java:103)
        at android.widget.AdapterView.performItemClick(AdapterView.java:298)
        at android.widget.AbsListView.performItemClick(AbsListView.java:1199)
        at android.widget.ListView.performItemClick(ListView.java:4444)
        at android.widget.AbsListView$PerformClick.run(AbsListView.java:3067)
        at android.widget.AbsListView$1.run(AbsListView.java:3753)
        at android.os.Handler.handleCallback(Handler.java:615)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:155)
        at android.app.ActivityThread.main(ActivityThread.java:5536)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1074)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:841)
        at dalvik.system.NativeStart.main(Native Method)

我无法弄清楚原因。 我在这里弄错了什么？

继承人的活动（缩减至最低版本）：

public class NewsList extends Activity {

    ListView newsHeaderList;
    LinearLayout backButton;
    TextView headerText;

    public NewsList()
    {
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_news_list);

        backButton = (LinearLayout)findViewById(R.id.backButton);
        headerText = (TextView)findViewById(R.id.headerText);

        newsHeaderList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                ReadNews(position);
            }
        });
    }

    private void SetNewsBackButton(Boolean visible)
    {
        RelativeLayout.LayoutParams params = (RelativeLayout.LayoutParams)headerText.getLayoutParams();
        if (visible)
        {
            backButton.setVisibility(View.VISIBLE);
            params.addRule(RelativeLayout.END_OF, R.id.backButton);
        } else {
            backButton.setVisibility(View.INVISIBLE);
            params.addRule(RelativeLayout.END_OF, 0);
        }
    }

    public void ReadNews(Integer guid)
    {
        SetNewsBackButton(true);
    }
}

继承人的观点XML Code（也有规定）：

<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:padding="0dp"
tools:context=".NewsList">

    <LinearLayout
        android:orientation="horizontal"
        android:layout_width="wrap_content"
        android:layout_height="75dp"
        android:id="@+id/backButton">

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/imageView"
            android:src="@drawable/headerbackbutton"
            android:layout_gravity="center_vertical" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="News"
            android:id="@+id/textView"
            android:layout_gravity="center_vertical"
            android:textColor="@color/colorheadertext"
            android:layout_marginLeft="-15dp" />
    </LinearLayout>

    <ImageView
        android:layout_width="wrap_content"
        android:layout_height="75dp"
        android:id="@+id/imageView2"
        android:src="@drawable/nfansheader"
        android:layout_alignParentTop="true"
        android:layout_alignParentRight="true" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="NFans.de - News"
        android:id="@+id/headerText"
        android:layout_toStartOf="@+id/imageView2"
        android:textColor="@color/colorheadertext"
        android:textStyle="bold"
        android:layout_centerVertical="true"
        android:layout_toEndOf="@+id/backButton"
        android:maxLines="1"
        android:singleLine="true"
        android:layout_toLeftOf="@+id/imageView2"
        android:layout_toRightOf="@+id/backButton"
        android:layout_marginLeft="5dp"
        android:layout_marginRight="-20dp" />
</RelativeLayout>

Answer 1

这些规则是在API级别17中引入的。如果在较旧的API上运行代码，则此ArrayIndexOutOfBoundsException将会崩溃。

/**
 * Rule that aligns a child's end edge with another child's start edge.
 */
public static final int START_OF                 = 16;
/**
 * Rule that aligns a child's start edge with another child's end edge.
 */
public static final int END_OF                   = 17;
/**
 * Rule that aligns a child's start edge with another child's start edge.
 */
public static final int ALIGN_START              = 18;
/**
 * Rule that aligns a child's end edge with another child's end edge.
 */
public static final int ALIGN_END                = 19;
/**
 * Rule that aligns the child's start edge with its RelativeLayout
 * parent's start edge.
 */
public static final int ALIGN_PARENT_START       = 20;
/**
 * Rule that aligns the child's end edge with its RelativeLayout
 * parent's end edge.
 */
public static final int ALIGN_PARENT_END         = 21;

对于那些较旧的API，您可以使用RIGHT而不是END和LEFT而不是START来解决此问题。 而不是removeRule(X)你可以调用addRule(X, 0)来清除规则。

样品：

        final boolean hasSdk17 = Build.VERSION.SDK_INT >= Build.VERSION_CODES.JELLY_BEAN_MR1;
        if (hasSdk17) {
            plateParams.removeRule(RelativeLayout.ABOVE);
            buttonsParams.addRule(RelativeLayout.ALIGN_BOTTOM, R.id.myView);
            buttonsParams.addRule(RelativeLayout.ALIGN_END, R.id.myView);
            buttonsParams.removeRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
        } else {
            plateParams.addRule(RelativeLayout.ABOVE, 0);
            buttonsParams.addRule(RelativeLayout.ALIGN_BOTTOM, R.id.myView);
            buttonsParams.addRule(RelativeLayout.ALIGN_RIGHT, R.id.myView);
            buttonsParams.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM, 0);
        }