第一个android教程不起作用:(

Question

我开始学习 Android 语言，我正在尝试做这个教程： http://developer.android.com/training/basics/firstapp/starting-activity.html

但我在“显示消息”部分有问题。

如果我添加这部分代码，当我按下发送按钮时，应用程序会强制关闭。

logcat（我不知道如何发布它：/）：

06-05 16:12:03.213: E/FragmentManager(11276): No view found for id 0x7f080000      (com.example.myfirstapp:id/container) for fragment PlaceholderFragment{41cce9e0 #0 id=0x7f080000}
06-05 16:12:03.213: E/FragmentManager(11276): Activity state:
06-05 16:12:03.221: E/FragmentManager(11276):   Local Activity 41cc61d0 State:
06-05 16:12:03.221: E/FragmentManager(11276):     mResumed=false mStopped=false    mFinished=false
06-05 16:12:03.221: E/FragmentManager(11276):     mLoadersStarted=false
06-05 16:12:03.221: E/FragmentManager(11276):     mChangingConfigurations=false
06-05 16:12:03.221: E/FragmentManager(11276):     mCurrentConfig={1.0 222mcc10mnc it_IT ldltr sw360dp w360dp h576dp 320dpi nrml long port finger -keyb/v/h -nav/h s.30 themeResource=null}
06-05 16:12:03.221: E/FragmentManager(11276):   Active Fragments in 41cc62c8:
06-05 16:12:03.229: E/FragmentManager(11276):     #0: PlaceholderFragment{41cce9e0 #0 id=0x7f080000}
06-05 16:12:03.229: E/FragmentManager(11276):       mFragmentId=#7f080000 mContainerId=#7f080000 mTag=null
06-05 16:12:03.229: E/FragmentManager(11276):       mState=0 mIndex=0 mWho=android:fragment:0 mBackStackNesting=0
06-05 16:12:03.229: E/FragmentManager(11276):       mAdded=true mRemoving=false mResumed=false mFromLayout=false mInLayout=false
06-05 16:12:03.229: E/FragmentManager(11276):       mHidden=false mDetached=false mMenuVisible=true mHasMenu=false
06-05 16:12:03.229: E/FragmentManager(11276):       mRetainInstance=false mRetaining=false mUserVisibleHint=true
06-05 16:12:03.229: E/FragmentManager(11276):       mFragmentManager=FragmentManager{41cc62c8 in DisplayMessageActivity{41cc61d0}}
06-05 16:12:03.229: E/FragmentManager(11276):       mActivity=com.example.myfirstapp.DisplayMessageActivity@41cc61d0
06-05 16:12:03.229: E/FragmentManager(11276):   Added Fragments:
06-05 16:12:03.229: E/FragmentManager(11276):     #0: PlaceholderFragment{41cce9e0 #0 id=0x7f080000}
06-05 16:12:03.229: E/FragmentManager(11276):   FragmentManager misc state:
06-05 16:12:03.229: E/FragmentManager(11276):     mActivity=
06-05 16:12:03.229: E/FragmentManager(11276): com.example.myfirstapp.DisplayMessageActivity@41cc61d0
06-05 16:12:03.229: E/FragmentManager(11276):     mContainer=android.app.Activity$1@41cc6340
06-05 16:12:03.229: E/FragmentManager(11276):     mCurState=2 mStateSaved=false mDestroyed=false
06-05 16:12:03.229: E/FragmentManager(11276):   Looper (main, tid 1) {41c68838}
06-05 16:12:03.229: E/FragmentManager(11276):     (Total messages: 0, idling=false, quitting=false)
06-05 16:12:03.236: E/AndroidRuntime(11276): FATAL EXCEPTION: main
06-05 16:12:03.236: E/AndroidRuntime(11276): Process: com.example.myfirstapp, PID: 11276
06-05 16:12:03.236: E/AndroidRuntime(11276): java.lang.RuntimeException: Unable to start activity    ComponentInfo{com.example.myfirstapp/com.example.myfirstapp.DisplayMessageActivity}: java.lang.IllegalArgumentException: No view found for id 0x7f080000 (com.example.myfirstapp:id/container) for fragment PlaceholderFragment{41cce9e0 #0 id=0x7f080000}
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2227)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2277)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.ActivityThread.access$800(ActivityThread.java:145)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)  
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.os.Handler.dispatchMessage(Handler.java:102)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.os.Looper.loop(Looper.java:136)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.ActivityThread.main(ActivityThread.java:5154)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at java.lang.reflect.Method.invokeNative(Native Method)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at java.lang.reflect.Method.invoke(Method.java:515)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at dalvik.system.NativeStart.main(Native Method)
06-05 16:12:03.236: E/AndroidRuntime(11276): Caused by: java.lang.IllegalArgumentException: No view found for id 0x7f080000 (com.example.myfirstapp:id/container) for fragment PlaceholderFragment{41cce9e0 #0 id=0x7f080000}
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:882)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1062)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.BackStackRecord.run(BackStackRecord.java:684)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1447)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.Activity.performStart(Activity.java:5319)
06-05 16:12:03.236: E/AndroidRuntime(11276):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2190)
 06-05 16:12:03.236: E/AndroidRuntime(11276):   ... 11 more

这是我认为有问题的代码部分：

public class DisplayMessageActivity extends Activity {

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

    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction()
                .add(R.id.container, new       PlaceholderFragment()).commit();
    }

    Intent intent = getIntent();
    String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);

    // Create the text view
    TextView textView = new TextView(this);
    textView.setTextSize(40);
    textView.setText(message);

    // Set the text view as the activity layout
    setContentView(textView);
}

事实上如果我删除了

 setContentView(textView);

新活动成功打开，明显没有字符串消息。

这是 fragment_display_message.xml

<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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.myfirstapp.DisplayMessageActivity$PlaceholderFragment" >

<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/hello_world" />

谢谢大家:)

Answer 1

java.lang.IllegalArgumentException: No view found for id 0x7f080000 (com.example.myfirstapp:id/container) for fragment PlaceholderFragment{41cce9e0 #0 id=0x7f080000}

当执行此处发布的片段事务时，您使用setContentView() 设置的内容视图没有片段容器视图：

getFragmentManager().beginTransaction()
  .add(R.id.container, new PlaceholderFragment()).commit();

container 可能实际上在您的 activity_main 布局中，但您稍后在 onCreate() 中将其替换为 TextView。

要么删除PlaceholderFragment 和片段事务，要么将TextView 放在活动或片段布局中，而不是在代码中动态创建它。

Answer 2

我在一个空白项目中尝试了您的代码，它运行良好：

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText("text");

        // Set the text view as the activity layout
        setContentView(textView);
    }
}

你忘记调用 super.onCreate 了吗？