Question

这是我正在处理的问题。

我正在尝试设置ViewPagers以加载3 XML个文件。我们称之为ViewPagerAdapter.java

在对象Instantiate上，我尝试使用findViewWithTag()更改所有文本字段字体。但是，如果使用EditText定义了findViewWithTag()，则会返回导致null错误的system.out.println（使用setTypeFace）。

我的代码做错了吗？

Object Instantiate Code (ViewPagerAdapter.java)

public Object instantiateItem(View collection, int position) {

        LayoutInflater inflater = (LayoutInflater) collection.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        int resId = 0;

        switch(position) {
        case 0:
            resId = R.layout.activity_login;
            break;
        case 1:
            resId = R.layout.activity_register;
            break;
        case 2:
            resId = R.layout.activity_vote;
            break;
        }
        View view = inflater.inflate(resId, null);
        EditText txtFields = (EditText) view.findViewWithTag("abeezee");
            txtFields.setTypeFace(Typeface.DEFAULT_BOLD); //This one cause the error (Line 39)
        System.out.println(txtFields);

        ((ViewPager) collection).addView(view, 0);
        return view;
    }

其中一个XML（activity_register.xml）：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/layRegister"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/transparent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin" >

    <TextView
        android:id="@+id/tvRegisterTitle"
        style="@style/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/etNameReg"
        android:layout_alignParentTop="true"
        android:text="@string/register_text"
        android:textAppearance="?android:attr/textAppearanceLarge" 
        />

    <EditText
        android:id="@+id/etNameReg"
        style="@style/textfield"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/spVoteMlm"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="15dp"
        android:ems="10"
        android:hint="@string/name_hint"
        android:inputType="textPersonName" 
        android:tag="abeezee"
        >

        <requestFocus />
    </EditText>

    <EditText
        android:id="@+id/etEmailReg"
        style="@style/textfield"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/etNameReg"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="15dp"
        android:ems="10"
        android:hint="@string/email_hint"
        android:inputType="textEmailAddress" 
        android:tag="abeezee"
        />

    <EditText
        android:id="@+id/etPasswordReg"
        style="@style/textfield"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/etEmailReg"
        android:layout_below="@+id/etEmailReg"
        android:layout_centerVertical="true"
        android:layout_marginTop="15dp"
        android:ems="10"
        android:hint="@string/password_hint"
        android:typeface="serif"
        android:inputType="textPassword" 
        android:tag="abeezee"
        />

    <Spinner
        android:id="@+id/spVoteMlm"
        style="@style/textfield"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_below="@+id/tvRegisterTitle"
        android:layout_marginTop="30dp"
        android:entries="@array/mlm_list" 
        android:tag="abeezee"
        />

    <Button
        android:id="@+id/btnRegister"
        style="@style/buttonBlue"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/btnTerms"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="15dp"
        android:text="@string/register_text" />

    <Button
        android:id="@+id/btnTerms"
        style="@style/smallLink"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/etPasswordReg"
        android:layout_centerHorizontal="true"
        android:gravity="center"   
        android:onClick="showTermsPolicy"
        android:text="@string/terms_policy" />

</RelativeLayout>

Logcat错误：

09-24 13:17:49.178: E/AndroidRuntime(16278): FATAL EXCEPTION: main
09-24 13:17:49.178: E/AndroidRuntime(16278): java.lang.NullPointerException
09-24 13:17:49.178: E/AndroidRuntime(16278):    at com.sociyo.ViewPagerAdapter.instantiateItem(ViewPagerAdapter.java:39)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.support.v4.view.PagerAdapter.instantiateItem(PagerAdapter.java:110)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:832)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.support.v4.view.ViewPager.populate(ViewPager.java:982)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.support.v4.view.ViewPager.populate(ViewPager.java:914)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1436)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.View.measure(View.java:15392)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:622)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:404)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.View.measure(View.java:15392)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4924)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:314)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.View.measure(View.java:15392)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4924)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1420)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:697)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:578)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.View.measure(View.java:15392)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:4924)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:314)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2154)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.View.measure(View.java:15392)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1865)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1113)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1286)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1011)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4244)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.Choreographer.doCallbacks(Choreographer.java:555)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.Choreographer.doFrame(Choreographer.java:525)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.os.Handler.handleCallback(Handler.java:615)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.os.Handler.dispatchMessage(Handler.java:92)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.os.Looper.loop(Looper.java:213)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at android.app.ActivityThread.main(ActivityThread.java:4793)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at java.lang.reflect.Method.invokeNative(Native Method)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at java.lang.reflect.Method.invoke(Method.java:511)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:789)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:556)
09-24 13:17:49.178: E/AndroidRuntime(16278):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

您可以使用以下getViewsByTag函数从父元素进行迭代，并获取它包含的所有“已标记”子元素。然后，您可以迭代这些视图并使用switch语句和instanceof来处理Button，EditText或TextView元素，如果您愿意的话。

public static ArrayList<View> getViewsByTag(ViewGroup root, String tag){
    ArrayList<View> views = new ArrayList<View>();
    final int childCount = root.getChildCount();
    for (int i = 0; i < childCount; i++) {
        final View child = root.getChildAt(i);
        if (child instanceof ViewGroup) {
            views.addAll(getViewsByTag((ViewGroup) child, tag));
        } 

        final Object tagObj = child.getTag();
        if (tagObj != null && tagObj.equals(tag)) {
            views.add(child);
        }

    }
    return views;
}

findViewWithTag返回null

1 个答案: