您好我试图在Android上创建我的第一个应用程序。抱歉愚蠢的问题，但我绝望了。
我在android studio中创建了带有空白活动的新应用程序。
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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
<TextView android:text="@string/hello_world" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</RelativeLayout>
爪哇：
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
.
.
.
}
然后我想将扩展的活动类更改为ListActivity：
public class MainActivity extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
.
.
.
}
当我在移动应用程序崩溃时运行它（没有其他更改），例如“应用程序xy已停止”。
我知道这是一些愚蠢的失败，但我不知道如何解决它。
清单：
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.kubitas.listviewapp" >
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:theme="@style/AppTheme" >
<activity
android:name=".MainActivity"
android:label="@string/app_name" >
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
请帮帮我。
答案 0 :(得分：2)
决定回答而不是评论：）
问题可能与ListActivity未扩展AppCompatActivity并且您可能正在使用支持库中的主题这一事实有关。我会切换回AppCompatActivity并改为使用android.support.v4.app.ListFragment片段。
另一个问题可能是ListActivity期望您的布局有ListView，其ID为“@android：id / list”
在我的某个应用程序中，我不想更改为ListFragment，因此我将AppCompactListActivity扩展为AppCompatActivity：
import android.os.Handler;
import android.view.View;
import android.view.animation.AnimationUtils;
import android.widget.AdapterView;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.TextView;
public abstract class AppCompatListActivity extends android.support.v7.app.AppCompatActivity {
static final int INTERNAL_EMPTY_ID = 0x00ff0001;
static final int INTERNAL_PROGRESS_CONTAINER_ID = 0x00ff0002;
static final int INTERNAL_LIST_CONTAINER_ID = 0x00ff0003;
final private Handler mHandler = new Handler();
final private Runnable mRequestFocus = new Runnable() {
public void run() {
mList.focusableViewAvailable(mList);
}
};
final private AdapterView.OnItemClickListener mOnClickListener
= new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
onListItemClick((ListView)parent, v, position, id);
}
};
ListAdapter mAdapter;
ListView mList;
View mEmptyView;
TextView mStandardEmptyView;
View mProgressContainer;
View mListContainer;
CharSequence mEmptyText;
boolean mListShown;
public AppCompatListActivity() {
}
/**
* Provide default implementation to return a simple list view. Subclasses
* can override to replace with their own layout. If doing so, the
* returned view hierarchy <em>must</em> have a ListView whose id
* is {@link android.R.id#list android.R.id.list} and can optionally
* have a sibling view id {@link android.R.id#empty android.R.id.empty}
* that is to be shown when the list is empty.
*
* <p>If you are overriding this method with your own custom content,
* consider including the standard layout {@link android.R.layout#list_content}
* in your layout file, so that you continue to retain all of the standard
* behavior of ListFragment. In particular, this is currently the only
* way to have the built-in indeterminant progress state be shown.
*/
/*
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
FrameLayout root = new FrameLayout(context);
// ------------------------------------------------------------------
LinearLayout pframe = new LinearLayout(context);
pframe.setId(INTERNAL_PROGRESS_CONTAINER_ID);
pframe.setOrientation(LinearLayout.VERTICAL);
pframe.setVisibility(View.GONE);
pframe.setGravity(Gravity.CENTER);
ProgressBar progress = new ProgressBar(context, null,
android.R.attr.progressBarStyleLarge);
pframe.addView(progress, new FrameLayout.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT));
root.addView(pframe, new FrameLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT));
// ------------------------------------------------------------------
FrameLayout lframe = new FrameLayout(context);
lframe.setId(INTERNAL_LIST_CONTAINER_ID);
TextView tv = new TextView(getActivity());
tv.setId(INTERNAL_EMPTY_ID);
tv.setGravity(Gravity.CENTER);
lframe.addView(tv, new FrameLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT));
ListView lv = new ListView(getActivity());
lv.setId(android.R.id.list);
lv.setDrawSelectorOnTop(false);
lframe.addView(lv, new FrameLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT));
root.addView(lframe, new FrameLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT));
// ------------------------------------------------------------------
root.setLayoutParams(new FrameLayout.LayoutParams(
ViewGroup.LayoutParams.FILL_PARENT, ViewGroup.LayoutParams.FILL_PARENT));
return root;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
ensureList();
}
*/
/**
* Detach from list view.
*/
@Override
public void onDestroy() {
mHandler.removeCallbacks(mRequestFocus);
mList = null;
mListShown = false;
mEmptyView = mProgressContainer = mListContainer = null;
mStandardEmptyView = null;
super.onDestroy();
}
/**
* This method will be called when an item in the list is selected.
* Subclasses should override. Subclasses can call
* getListView().getItemAtPosition(position) if they need to access the
* data associated with the selected item.
*
* @param l The ListView where the click happened
* @param v The view that was clicked within the ListView
* @param position The position of the view in the list
* @param id The row id of the item that was clicked
*/
public void onListItemClick(ListView l, View v, int position, long id) {
}
/**
* Provide the cursor for the list view.
*/
public void setListAdapter(ListAdapter adapter) {
boolean hadAdapter = mAdapter != null;
mAdapter = adapter;
if (mList != null) {
mList.setAdapter(adapter);
if (!mListShown && !hadAdapter) {
// The list was hidden, and previously didn't have an
// adapter. It is now time to show it.
//setListShown(true, getView().getWindowToken() != null);
setListShown(true, false);
}
}
}
/**
* Set the currently selected list item to the specified
* position with the adapter's data
*
* @param position -
*/
public void setSelection(int position) {
ensureList();
mList.setSelection(position);
}
/**
* Get the position of the currently selected list item.
*/
public int getSelectedItemPosition() {
ensureList();
return mList.getSelectedItemPosition();
}
/**
* Get the cursor row ID of the currently selected list item.
*/
public long getSelectedItemId() {
ensureList();
return mList.getSelectedItemId();
}
/**
* Get the activity's list view widget.
*/
public ListView getListView() {
ensureList();
return mList;
}
/**
* The default content for a ListFragment has a TextView that can
* be shown when the list is empty. If you would like to have it
* shown, call this method to supply the text it should use.
*/
public void setEmptyText(CharSequence text) {
ensureList();
if (mStandardEmptyView == null) {
throw new IllegalStateException("Can't be used with a custom content view");
}
mStandardEmptyView.setText(text);
if (mEmptyText == null) {
mList.setEmptyView(mStandardEmptyView);
}
mEmptyText = text;
}
/**
* Control whether the list is being displayed. You can make it not
* displayed if you are waiting for the initial data to show in it. During
* this time an indeterminant progress indicator will be shown instead.
*
* <p>Applications do not normally need to use this themselves. The default
* behavior of ListFragment is to start with the list not being shown, only
* showing it once an adapter is given with {@link #setListAdapter(ListAdapter)}.
* If the list at that point had not been shown, when it does get shown
* it will be do without the user ever seeing the hidden state.
*
* @param shown If true, the list view is shown; if false, the progress
* indicator. The initial value is true.
*/
public void setListShown(boolean shown) {
setListShown(shown, true);
}
/**
* Like {@link #setListShown(boolean)}, but no animation is used when
* transitioning from the previous state.
*/
public void setListShownNoAnimation(boolean shown) {
setListShown(shown, false);
}
/**
* Control whether the list is being displayed. You can make it not
* displayed if you are waiting for the initial data to show in it. During
* this time an indeterminant progress indicator will be shown instead.
*
* @param shown If true, the list view is shown; if false, the progress
* indicator. The initial value is true.
* @param animate If true, an animation will be used to transition to the
* new state.
*/
private void setListShown(boolean shown, boolean animate) {
ensureList();
if (mProgressContainer == null) {
throw new IllegalStateException("Can't be used with a custom content view");
}
if (mListShown == shown) {
return;
}
mListShown = shown;
if (shown) {
if (animate) {
mProgressContainer.startAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_out));
mListContainer.startAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_in));
} else {
mProgressContainer.clearAnimation();
mListContainer.clearAnimation();
}
mProgressContainer.setVisibility(View.GONE);
mListContainer.setVisibility(View.VISIBLE);
} else {
if (animate) {
mProgressContainer.startAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_in));
mListContainer.startAnimation(AnimationUtils.loadAnimation(this, android.R.anim.fade_out));
} else {
mProgressContainer.clearAnimation();
mListContainer.clearAnimation();
}
mProgressContainer.setVisibility(View.VISIBLE);
mListContainer.setVisibility(View.GONE);
}
}
/**
* Get the ListAdapter associated with this activity's ListView.
*/
public ListAdapter getListAdapter() {
return mAdapter;
}
private void ensureList() {
if (mList != null) {
return;
}
View root = findViewById(android.R.id.content).getRootView();
if (root == null) {
throw new IllegalStateException("Content view not yet created");
}
if (root instanceof ListView) {
mList = (ListView)root;
} else {
mStandardEmptyView = (TextView)root.findViewById(INTERNAL_EMPTY_ID);
if (mStandardEmptyView == null) {
mEmptyView = root.findViewById(android.R.id.empty);
} else {
mStandardEmptyView.setVisibility(View.GONE);
}
mProgressContainer = root.findViewById(INTERNAL_PROGRESS_CONTAINER_ID);
mListContainer = root.findViewById(INTERNAL_LIST_CONTAINER_ID);
View rawListView = root.findViewById(android.R.id.list);
if (!(rawListView instanceof ListView)) {
if (rawListView == null) {
throw new RuntimeException(
"Your content must have a ListView whose id attribute is " +
"'android.R.id.list'");
}
throw new RuntimeException(
"Content has view with id attribute 'android.R.id.list' "
+ "that is not a ListView class");
}
mList = (ListView)rawListView;
if (mEmptyView != null) {
mList.setEmptyView(mEmptyView);
} else if (mEmptyText != null) {
mStandardEmptyView.setText(mEmptyText);
mList.setEmptyView(mStandardEmptyView);
}
}
mListShown = true;
mList.setOnItemClickListener(mOnClickListener);
if (mAdapter != null) {
ListAdapter adapter = mAdapter;
mAdapter = null;
setListAdapter(adapter);
} else {
// We are starting without an adapter, so assume we won't
// have our data right away and start with the progress indicator.
if (mProgressContainer != null) {
setListShown(false, false);
}
}
mHandler.post(mRequestFocus);
}
}
大部分代码都是从ListFragment实施中借用的，这就是为什么您会看到已注释掉onCreateView和onViewCreated方法的原因。
答案 1 :(得分：1)
ListActivity必须在名为的活动中声明一个列表：＆＃34; @android：id / list＆＃34;。这是使用ListActivity的要求。如果您没有真正使用ListActivity，则需要扩展Activity或AppCompatActivity。如果你想要使用ListActivity，那么在你的布局文件中添加一个ListView，并按照我的名字命名。
请参阅：http://developer.android.com/reference/android/app/ListActivity.html
<?xml version="1.0" encoding="utf-8"?>
<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:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">
<ListView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@android:id/list"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true" />
</RelativeLayout>
扩展ListActivity的类
public class MainActivity extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}