Question

以下是MainActivity.java之后的onCreate，仅包含几个if/else块：

// Simple array with a list of languages
    String[] languages = {"Arabic", "Armenian", "Cantonese", "Cherokee",
            "Czech", "Dutch", "English", "French", "Gaelic", "German",
            "Greek", "Haitian Creole", "Hawaiian", "Italian", "Japanese", "Korean",
            "Mandarin", "Navajo", "Philippines Tagalog", "Polish", "Portuguese", "Romanian",
            "Russian", "Spanish", "Swedish", "Vietnamese"};

    // Simple array with a list of the spelling for Merry Christmas in language 
    final String[] merrychristmas = {"Eid Melad Majeed", "Shnorhavor Surb Tsnund",
            "Sing-daan Faai-lohk", "ulihelisdi hunadetiyisgvi", "veselé vánoce",
            "vrolijk kerstfeest", "Merry Christmas!", "joyeux Noël", "Nollaig Shona Duit",
            "frohe Weihnacten", "Kalá Christoúgenna", "Jwaye Nwèl", "Mele Kalikimaka",
            "Buon Natale", "Merīkurisumasu", "jilgohun-christmas-bonoseyo",
            "Shèndàn kuàilè", "Nizhónígo Késhmish Da'doohleel", 
            "Mąligayang Pasko", "Wesołych Świąt", "Feliz Natal", "Crăcuin fericit",
            "schastlivogo Rozhdestva", "Feliz Navidad", "god jul", "Chúc Mừng Giáng Sinh"};

    CustomAdapter adapter = new CustomAdapter();
    listView1 = (ListView) findViewById(R.id.listView1);
    View header = (View) getLayoutInflater().inflate(R.layout.listview_header_row, null);
    listView1.addHeaderView(header);
    listView1.setAdapter(adapter);
    listView1.setOnItemClickListener(new AdapterView.OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View v, int position, long id) {
            String selectedLanguage = (String) listView1.getItemAtPosition(position);
            LinearLayout layout = new LinearLayout(MainActivity.this);
            layout.setBackgroundResource(R.drawable.circle);

            TextView tv = new TextView(MainActivity.this);
            // set the TextView properties
            tv.setTextColor(Color.WHITE);
            tv.setTextSize(20);
            tv.setPaddingRelative(22,108,0,0);
            tv.setGravity(Gravity.FILL);
            tv.setText(merrychristmas[position]);
            layout.addView(tv);
            Toast toast = new Toast(MainActivity.this);

            if (position == 0) {
                Toast.makeText(getApplicationContext(),
                        merrychristmas[position], LENGTH_LONG);
                // set the layout as the toast view
                toast.setView(layout);
               toast.setGravity(Gravity.CENTER_HORIZONTAL, 0, 0);
               toast.show();
                _player = MediaPlayer.create(MainActivity.this, R.raw.arabic);
                _player.start();
            } else if (position == 1) {
                Toast.makeText(getApplicationContext(),
                        merrychristmas[position], LENGTH_LONG);
                // set the layout as the toast view
                toast.setView(layout);
                toast.setGravity(Gravity.CENTER_HORIZONTAL, 0, 0);
                toast.show();
                _player = MediaPlayer.create(MainActivity.this, R.raw.armenian);
                _player.start();

这是我尝试实现的自定义适配器，用于更改listview的文本颜色（使用黑色文本可以正常工作！）

public class CustomAdapter extends BaseAdapter {
public String rowText;
Context context;
int layoutResourceId;
// Simple array with a list of languages
String[] languages = {"Arabic", "Armenian", "Cantonese", "Cherokee",
        "Czech", "Dutch", "English", "French", "Gaelic", "German",
        "Greek", "Haitian Creole", "Hawaiian", "Italian", "Japanese", "Korean",
        "Mandarin", "Navajo", "Philippines Tagalog", "Polish", "Portuguese", "Romanian",
        "Russian", "Spanish", "Swedish", "Vietnamese"};
LayoutInflater mInflater = ((Activity)context).getLayoutInflater();
@Override
public int getCount() {
    return languages.length;
}
@Override
public Object getItem(int position) {
    return languages[position];
}
@Override
public long getItemId(int position) {
    return(position);
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {

    ViewHolder holder;
    if (convertView == null) {
        convertView = mInflater.inflate(R.layout.listview_item_row, null);
        holder = new ViewHolder();
        holder.rowText = (TextView) convertView.findViewById(R.id.textView1);
        convertView.setTag(holder);
    } else {
        holder = (ViewHolder) convertView.getTag();
    }
    holder.rowText.setText(languages[position]);
    holder.rowText.setBackgroundResource(R.color.xmas_green);
    return convertView;
}
public class ViewHolder {
    TextView rowText;
}
}

这是activity_main.xml

<ListView
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:id="@+id/listView1"
android:divider="@android:color/white"
android:dividerHeight="1dp">
</ListView>

<View android:layout_width="50dp"
      android:layout_height="50dp"
      android:background="@drawable/circle" />

</LinearLayout>

这是标题行布局：

<TextView
    android:id="@+id/txtHeader"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:textSize="22sp"
    android:padding="10dp"
    android:textStyle="bold"
    android:textColor="@color/white"
    android:background="@color/xmas_green"
    android:text="Click on a language to listen"
    android:focusable="false"
    android:focusableInTouchMode="false"/>

这是项目行布局：

<TextView
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:gravity="center_vertical"
    android:textSize="18sp"
    android:textColor="@color/white"
    android:id="@+id/txtLanguage"/>

</LinearLayout>

这是mylist_layout.xml

<TextView
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:id="@+id/textView1"
    android:textColor="@color/white"
    android:textSize="20sp"
    android:paddingTop="10dp"
    android:paddingBottom="10dp"/>

</LinearLayout>

最后，这是toast_view.xml：`

<View android:layout_width="match_parent"
    android:layout_height="fill_parent"
    android:background="@drawable/circle" >

</View>

</LinearLayout>

我完成了项目＆gt;清洁然后重建多次。我没有触摸清单文件。（看，我一直在研究这个可爱的信息保险库！）在此先感谢，我很感激你的帮助！

这是LogCat输出....谢谢！

    10-04 15:00:02.780      865-865/com.blogspot.joyouslybeingjoy.merryxmasindifflangs
D/dalvikvm﹕ Not late-enabling CheckJNI (already on)
10-04 15:00:06.230      865-865/com.blogspot.joyouslybeingjoy.merryxmasindifflangs 
D/dalvikvm﹕ GC_FOR_ALLOC freed 48K, 5% free 2949K/3076K, paused 47ms, total 49ms
10-04 15:00:06.230      865-865/com.blogspot.joyouslybeingjoy.merryxmasindifflangs
I/dalvikvm-heap﹕ Grow heap (frag case) to 3.559MB for 635812-byte allocation
10-04 15:00:06.340      865-865/com.blogspot.joyouslybeingjoy.merryxmasindifflangs 
D/dalvikvm﹕ GC_FOR_ALLOC freed 0K, 4% free 3570K/3700K, paused 39ms, total 39ms
10-04 15:00:06.410      865-865/com.blogspot.joyouslybeingjoy.merryxmasindifflangs 
D/AndroidRuntime﹕ Shutting down VM
10-04 15:00:06.410      865-865/com.blogspot.joyouslybeingjoy.merryxmasindifflangs 
W/dalvikvm﹕ threadid=1: thread exiting with uncaught exception (group=0xb3ababa8)
10-04 15:00:06.430      865-865/com.blogspot.joyouslybeingjoy.merryxmasindifflangs 
E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.blogspot.joyouslybeingjoy.merryxmasindifflangs, PID: 865
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.blogspot.
joyouslybeingjoy.
merryxmasindifflangs/com.blogspot.joyouslybeingjoy.merryxmasindifflangs.MainActivity}: 
java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2195)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
        at android.app.ActivityThread.access$800(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at com.blogspot.joyouslybeingjoy.merryxmasindifflangs.CustomAdapter.<init>
        (CustomAdapter.java:27)
        at com.blogspot.joyouslybeingjoy.merryxmasindifflangs.MainActivity.onCreate
        (MainActivity.java:81)
        at android.app.Activity.performCreate(Activity.java:5231)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2159)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2245)
        at android.app.ActivityThread.access$800(ActivityThread.java:135)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1196)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5017)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
        at dalvik.system.NativeStart.main(Native Method)
10-04 15:00:09.430      865-865/com.blogspot.joyouslybeingjoy.merryxmasindifflangs 
I/Process﹕ 
Sending signal. PID: 865 SIG: 9

Answer 1

您的问题位于CustomAdapter.java的第27行让我假设 - 第27行是：

 LayoutInflater mInflater = ((Activity)context).getLayoutInflater();

因此(Activity)context在实例初始化过程中null会让您遇到问题。

的修改
将初始化移动到构造函数。如果需要 - 在那里传递上下文参数

致命异常无法启动活动

1 个答案: