java之使用findViewByID时，使用充气器的Android应用程序为空

我正在开发我的第一个Android应用程序。当我添加了在OnCreate和onRestart上保存和加载对象和设置的功能时，该应用在启动时开始崩溃。

这是我为设置内容而编写的代码

public void setSettings() { 
    SharedPreferences settings = getSharedPreferences("Prefs", 0); 
    newGame = settings.getBoolean("newGame", true); 
    autoDecide = settings.getBoolean("autoDecide", true); 
    saved = settings.getBoolean("saved", false); 
 
    if (saved) { 
        player1 = readPlayer("Player 1"); 
        player2 = readPlayer("Player 2"); 
        if (player1 != null && player2 != null) { 
            ((TextView) findViewById(R.id.Player1name)).setText("" + player1.name); 
            ((TextView) findViewById(R.id.Player2name)).setText("" + player2.name); 
            ((TextView) findViewById(R.id.player1wins)).setText("" + player1.totalWins); 
            ((TextView) findViewById(R.id.player2wins)).setText("" + player2.totalWins); 
            ((TextView) findViewById(R.id.Player1life)).setText("" + player1.life); 
            ((TextView) findViewById(R.id.Player2life)).setText("" + player2.life); 
        } 
 
    } 

logCat显示的NullPointerException指向第一个findViewByID(R.id.Player1name)。我尝试只传递一个普通的String，但仍然得到一个nullPointer，所以我知道它是findViewById。

这是调用它的OnCreate

    public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    ViewPagerAdapter adapter= new ViewPagerAdapter(); 
    ViewPager pager = (ViewPager)findViewById(R.id.viewpager); 
    TitlePageIndicator indicator = (TitlePageIndicator)findViewById(R.id.indicator); 
    pager.setAdapter(adapter); 
    indicator.setViewPager(pager); 
    pager.setCurrentItem(1); 
    setSettings(); 
 
}  

我的应用程序使用ViewPagerIndicator，因此有人不能找到它吗？

这是代码的主要部分，它使用ViewPager并切换 View 。

public class ViewPagerAdapter extends PagerAdapter implements TitleProvider{ 
private static String[] titles = new String[]{"Settings", "2 Players"}; 
 
@Override 
public int getCount() { 
    return titles.length; 
} 
public Object instantiateItem(View collection, int position){ 
    LayoutInflater inflator = (LayoutInflater) collection.getContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
    int resID = 0; 
    switch (position){ 
    case 0: 
        resID = R.layout.settings; 
        break; 
    case 1: 
        resID = R.layout.two_player; 
        break; 
    } 
    View view = inflator.inflate(resID, null); 
    ((ViewPager)collection).addView(view, 0); 
    return view; 
} 

这是首次创建时应该在其上的布局。

### Layout XML ### 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" 
android:layout_height="match_parent" > 
<TextView 
        android:id="@+id/Player1name" 
        android:layout_width="125dp" 
        android:layout_height="wrap_content" 
        android:layout_alignParentLeft="true" 
        android:layout_alignParentTop="true" 
        android:layout_marginLeft="34dp" 
        android:layout_marginTop="35dp" 
        android:text="@string/player1" 
        android:textAppearance="?android:attr/textAppearanceLarge" /> 
 
    <TextView 
        android:id="@+id/Player2name" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_alignParentTop="true" 
        android:layout_alignParentRight="true" 
        android:layout_marginRight = "34dp" 
        android:layout_marginTop="35dp" 
        android:text="@string/player2" 
        android:textAppearance="?android:attr/textAppearanceLarge" /> 
 
    <TextView 
        android:id="@+id/Player1life" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_alignLeft="@+id/Player1name" 
        android:layout_below="@+id/Player1name" 
        android:layout_marginLeft="20dp" 
        android:layout_marginTop="16dp" 
        android:text="@string/player1life" 
        android:textAppearance="?android:attr/textAppearanceLarge" 
        android:textSize="28sp" /> 
 
 
    <TextView 
        android:id="@+id/Player2life" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_above="@+id/player1add" 
        android:layout_alignRight="@+id/Player2name" 
        android:text="@string/player2life" 
        android:textAppearance="?android:attr/textAppearanceLarge" 
        android:textSize="28sp" />         
 
    <TableLayout 
        android:id="@+id/player1add" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_alignParentLeft="true" 
        android:layout_below="@+id/Player1life" 
        android:layout_marginLeft="15dp" 
        android:layout_marginTop="16dp" > 
 
        <TableRow 
            android:id="@+id/p1add1" 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" > 
 
            <Button 
                android:id="@+id/player1add1000" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player1add1000" 
                android:text="@string/add1000" /> 
 
            <Button 
                android:id="@+id/player1add500" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player1add500" 
                android:text="@string/add500" /> 
        </TableRow> 
 
        <TableRow 
            android:id="@+id/p1add2" 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" > 
 
            <Button 
                android:id="@+id/player1add100" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player1add100" 
                android:text="@string/add100" /> 
 
            <Button 
                android:id="@+id/player1add50" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player1add50" 
                android:text="@string/add50" /> 
        </TableRow> 
    </TableLayout> 
 
    <TableLayout 
        android:id="@+id/player2add" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_alignTop="@+id/player1add" 
        android:layout_alignParentRight = "true" 
        android:layout_marginRight = "15dp" > 
 
        <TableRow 
            android:id="@+id/p2add1" 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" > 
 
            <Button 
                android:id="@+id/player2add1000" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player2add1000" 
                android:text="@string/add1000" /> 
 
            <Button 
                android:id="@+id/player2add500" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player2add500" 
                android:text="@string/add500" /> 
        </TableRow> 
 
        <TableRow 
            android:id="@+id/p2add2" 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" > 
 
            <Button 
                android:id="@+id/player2add100" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player2add100" 
                android:text="@string/add100" /> 
 
            <Button 
                android:id="@+id/player2add50" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player2add50" 
                android:text="@string/add50" /> 
        </TableRow> 
    </TableLayout> 
 
    <TableLayout 
        android:id="@+id/player1sub" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_alignParentLeft="true" 
        android:layout_alignTop="@+id/player1add" 
        android:layout_marginTop="133dp"  
        android:layout_marginLeft="16dp"> 
 
 
        <TableRow 
            android:id="@+id/p1sub1" 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" > 
 
            <Button 
                android:id="@+id/player1sub1000" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player1sub1000" 
                android:text="@string/sub1000" /> 
 
            <Button 
                android:id="@+id/player1sub500" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player1sub500" 
                android:text="@string/sub500" /> 
        </TableRow> 
 
        <TableRow 
            android:id="@+id/p1sub2" 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" > 
 
            <Button 
                android:id="@+id/player1sub100" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player1sub100" 
                android:text="@string/sub100" /> 
 
            <Button 
                android:id="@+id/player1sub50" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player1sub50" 
                android:text="@string/sub50" /> 
        </TableRow> 
    </TableLayout> 
 
    <TableLayout 
        android:id="@+id/player2sub" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_alignTop="@+id/player1sub" 
        android:layout_alignParentRight = "true" 
        android:layout_marginRight =  "15dp"> 
 
 
        <TableRow 
            android:id="@+id/p2sub1" 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" > 
 
            <Button 
                android:id="@+id/player2sub1000" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player2sub1000" 
                android:text="@string/sub1000" /> 
 
            <Button 
                android:id="@+id/player2sub500" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player2sub500" 
                android:text="@string/sub500" /> 
        </TableRow> 
 
        <TableRow 
            android:id="@+id/p2sub2" 
            android:layout_width="wrap_content" 
            android:layout_height="wrap_content" > 
 
            <Button 
                android:id="@+id/player2sub100" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player2sub100" 
                android:text="@string/sub100" /> 
 
            <Button 
                android:id="@+id/player2sub50" 
                android:layout_width="wrap_content" 
                android:layout_height="wrap_content" 
                android:onClick="Player2sub50" 
                android:text="@string/sub50" /> 
        </TableRow> 
    </TableLayout> 
 
    <Button 
        android:id="@+id/reset" 
        android:layout_width="wrap_content" 
        android:layout_height="wrap_content" 
        android:layout_below="@+id/player1sub" 
        android:layout_marginTop="30dp" 
        android:layout_centerInParent="true" 
        android:onClick="reset" 
        android:text="@string/reset" /> 

我检查了一下，但是我确实设置了setContentView，并且尝试清理项目，所以我不知道有什么问题。

请您参考如下方法:

如下更新您的onCreate(Bundle savedInstanceState)方法，这可能对您有帮助

public void onCreate(Bundle savedInstanceState) { 
        super.onCreate(savedInstanceState); 
        setContentView(R.layout.main); 
        ViewPagerAdapter adapter= new ViewPagerAdapter(); 
        ViewPager pager = (ViewPager)findViewById(R.id.viewpager); 
        TitlePageIndicator indicator = (TitlePageIndicator)findViewById(R.id.indicator); 
        pager.setAdapter(adapter); 
        indicator.setViewPager(pager); 
        pager.setCurrentItem(1); 
 
        // added by subodh  
        TextView txtView1 = ((TextView) findViewById(R.id.Player1name)); 
        TextView txtView2 = ((TextView) findViewById(R.id.Player2name)); 
        TextView txtView3 = ((TextView) findViewById(R.id.player1wins)); 
        TextView txtView4 = ((TextView) findViewById(R.id.player2wins)); 
        TextView txtView5 = ((TextView) findViewById(R.id.Player1life)); 
        TextView txtView6 = ((TextView) findViewById(R.id.Player2life)); 
 
        setSettings(txtView1,txtView2,txtView3,txtView4,txtView5,txtView6); 
 
    } 

编辑第二种方法:

public void setSettings(TextView txtView1,TextView txtView2,TextView txtView3,TextView txtView4,TextView txtView5,TextView txtView6) { 
        SharedPreferences settings = getSharedPreferences("Prefs", 0); 
        newGame = settings.getBoolean("newGame", true); 
        autoDecide = settings.getBoolean("autoDecide", true); 
        saved = settings.getBoolean("saved", false); 
 
        if (saved) { 
            player1 = readPlayer("Player 1"); 
            player2 = readPlayer("Player 2"); 
            if (player1 != null && player2 != null)  
            { 
                txtView1.setText("" + player1.name); 
                txtView2.setText("" + player2.name); 
                txtView3.setText("" + player1.totalWins); 
                txtView4.setText("" + player2.totalWins); 
                txtView5.setText("" + player1.life); 
                txtView6.setText("" + player2.life); 
 
 
            } 
 
        } 
 
}