android - findViewById 在扩展的 LinearLayout 中返回 null

Question

我有一个自定义线性布局，如下所示:

public class CheckedLinearLayout extends LinearLayout implements Checkable {
    private RadioButton mRadio;

    public CheckedLinearLayout(Context context, AttributeSet attributeSet){
        super(context, attributeSet);
        LayoutInflater inflater = LayoutInflater.from(context);
        inflater.inflate(R.layout.list_item, null);
        this.mRadio = (RadioButton)findViewById(R.id.radio_button);
    }
}

但是 findViewById 总是返回 null。

xml:

<?xml version="1.0" encoding="utf-8"?>
<derongan.upper.CheckedLinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal" android:layout_width="match_parent"
android:layout_height="wrap_content">

<TextView
    android:id="@+id/count_type"
    android:layout_width="0dp"
    android:layout_weight="1"
    android:layout_height="match_parent" />

<EditText
    android:id="@+id/edit_text"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="1"
    android:hint="New Counter"
    android:visibility="gone"/>

<RadioButton
    android:id="@+id/radio_button"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"/>
</derongan.upper.CheckedLinearLayout>

为什么 findViewById 总是返回 null，我该如何正确调用它？我是否夸大了观点错误？

编辑:

当我添加

View view = inflater.inflate(...)

我收到一个新错误(这似乎与内存问题有关？)

09-19 23:53:22.760     982-1015/? E/SurfaceFlinger﹕ ro.sf.lcd_density must 

be defined as a build property
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115] JNI ERROR (app bug): local reference table overflow (max=512)
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115] local reference table dump:
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]   Last 10 entries (of 512):
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       511: 0x12c918b0 derongan.upper.UpperWidgetConfigure
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       510: 0x12d735e0 java.lang.String "derongan.upper.C... (34 chars)
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       509: 0x12c918b0 derongan.upper.UpperWidgetConfigure
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       508: 0x12e74800 derongan.upper.CheckedLinearLayout
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       507: 0x12e74400 derongan.upper.CheckedLinearLayout
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       506: 0x12e74000 derongan.upper.CheckedLinearLayout
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       505: 0x12e73c00 derongan.upper.CheckedLinearLayout
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       504: 0x12e73800 derongan.upper.CheckedLinearLayout
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       503: 0x12e73400 derongan.upper.CheckedLinearLayout
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       502: 0x12e72c00 derongan.upper.CheckedLinearLayout
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]   Summary:
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]       503 of derongan.upper.CheckedLinearLayout (503 unique instances)
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]         2 of derongan.upper.UpperWidgetConfigure (1 unique instances)
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]         2 of java.lang.Class (2 unique instances)
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]         1 of java.lang.String[] (3 elements)
09-19 23:53:22.856  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]         4 of java.lang.String (4 unique instances)
09-19 23:53:22.857  11757-11757/derongan.upper A/art﹕ art/runtime/indirect_reference_table.cc:115]
09-19 23:53:23.520  11757-11757/derongan.upper A/art﹕ art/runtime/barrier.cc:90] Check failed: count_ == 0 (count_=-1, 0=0) Attempted to destroy barrier with non zero count
09-19 23:53:23.520  11757-11757/derongan.upper A/art﹕ art/runtime/runtime.cc:366] Runtime aborting --- recursively, so no thread-specific detail!
09-19 23:53:23.520  11757-11757/derongan.upper A/art﹕ art/runtime/runtime.cc:366]
09-19 23:53:23.520  11757-11757/derongan.upper A/libc﹕ Fatal signal 6 (SIGABRT), code -6 in tid 11757 (derongan.upper)
09-19 23:53:23.658    4490-4490/? A/DEBUG﹕ *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
09-19 23:53:23.658    4490-4490/? A/DEBUG﹕ Build fingerprint: 'generic_x86/sdk_google_phone_x86/generic_x86:6.0/MRA44C/2166767:eng/test-keys'
09-19 23:53:23.658    4490-4490/? A/DEBUG﹕ Revision: '0'
09-19 23:53:23.658    4490-4490/? A/DEBUG﹕ ABI: 'x86'
09-19 23:53:23.658    4490-4490/? A/DEBUG﹕ pid: 11757, tid: 11757, name: derongan.upper  >>> derongan.upper <<<
09-19 23:53:23.658    4490-4490/? A/DEBUG﹕ signal 6 (SIGABRT), code -6 (SI_TKILL), fault addr --------
09-19 23:53:23.661    4490-4490/? A/DEBUG﹕ Abort message: 'art/runtime/indirect_reference_table.cc:115] JNI ERROR (app bug): local reference table overflow (max=512)'
09-19 23:53:23.661    4490-4490/? A/DEBUG﹕ eax 00000000  ebx 00002ded  ecx 00002ded  edx 00000006
09-19 23:53:23.661    4490-4490/? A/DEBUG﹕ esi b77b8c50  edi 00000002
09-19 23:53:23.661    4490-4490/? A/DEBUG﹕ xcs 00000073  xds 0000007b  xes 0000007b  xfs 00000007  xss 0000007b
09-19 23:53:23.661    4490-4490/? A/DEBUG﹕ eip b73815d6  ebp 00002ded  esp bfe3adb0  flags 00200206
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ backtrace:
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #00 pc 000845d6  /system/lib/libc.so (tgkill+22)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #01 pc 00081618  /system/lib/libc.so (pthread_kill+70)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #02 pc 00027205  /system/lib/libc.so (raise+36)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #03 pc 000209e4  /system/lib/libc.so (abort+80)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #04 pc 0051753b  /system/lib/libart.so (art::Runtime::Abort()+377)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #05 pc 0014d9f3  /system/lib/libart.so (art::LogMessage::~LogMessage()+1343)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #06 pc 00147f36  /system/lib/libart.so (art::Barrier::~Barrier()+966)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #07 pc 0056027f  /system/lib/libart.so (art::ThreadList::Dump(std::__1::basic_ostream<char, std::__1::char_traits<char> >&)+271)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #08 pc 005176b8  /system/lib/libart.so (art::Runtime::Abort()+758)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #09 pc 0014d9f3  /system/lib/libart.so (art::LogMessage::~LogMessage()+1343)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #10 pc 002e70ac  /system/lib/libart.so (art::IndirectReferenceTable::Add(unsigned int, art::mirror::Object*)+860)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #11 pc 00664ec1  /system/lib/libart.so (art::RememberForGcArgumentVisitor::Visit()+89)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #12 pc 0066523b  /system/lib/libart.so (art::QuickArgumentVisitor::VisitArguments() (.constprop.257)+223)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #13 pc 00669ed4  /system/lib/libart.so (artQuickResolutionTrampoline+1060)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #14 pc 0013d7fd  /system/lib/libart.so (art_quick_resolution_trampoline+77)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #15 pc 005cbc10  /data/app/derongan.upper-1/oat/x86/base.odex (android.view.View android.support.v4.app.FragmentActivity.onCreateView(java.lang.String, android.content.Context, android.util.AttributeSet)+84)
09-19 23:53:23.663    4490-4490/? A/DEBUG﹕ #16 pc 7416d2b7  /data/dalvik-cache/x86/system@framework@boot.oat
09-19 23:53:23.830    4490-4490/? A/DEBUG﹕ Tombstone written to: /data/tombstones/tombstone_09
09-19 23:53:23.830    4490-4490/? E/DEBUG﹕ AM write failed: Broken pipe
09-19 23:53:23.856    1291-1331/system_process E/InputDispatcher﹕ channel 'd69290f derongan.upper/derongan.upper.UpperWidgetConfigure (server)' ~ Channel is unrecoverably broken and will be disposed!
09-19 23:53:24.095    2203-2203/com.android.launcher3 E/Launcher﹕ Error: appWidgetId (EXTRA_APPWIDGET_ID) was not returned from the widget configuration activity.

Answer 1

这里有两件事你必须做。

首先，在您的代码中，替换:

inflater.inflate(R.layout.list_item, null);

与:

inflater.inflate(R.layout.list_item, this);

通过这种方式，您将告诉充气器将充气 View 附加到您的层次结构中。提供一个 null 参数将使膨胀的 View 在没有父级的情况下 float 。

其次，在您的 xml 标记中，替换:

derongan.upper.CheckedLinearLayout

用一个简单的

LinearLayout

通过这样做，您将避免递归地重新创建您的 View (不幸的是，在您的自定义 View 布局上调用 inflate 将调用它的 xml 构造函数，并且在同一个构造函数中调用 inflate 会给您带来溢出错误)。只需在 xml 中使用 LinearLayout 或为您的 View 提供两种类型的构造函数。