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Android AlertDialog因NullPointerException而崩潰

[英]Android AlertDialog crashes with NullPointerException

 原文  2014-06-12 05:30:37  8   3    java/ android/ nullpointerexception/ android-alertdialog

問題描述

我嘗試將HTML放入AlertDialog中的Listviewitem中。 因此，我找到了一些代碼片段，最后將它們與AlertDialog一起設置了。 

AlertDialog.Builder builder = new AlertDialog.Builder(ChatActivity.this);
            builder.setTitle("Onlineliste");

            final LayoutInflater inflater = getLayoutInflater();
            final View convertView2 = (View) inflater.inflate(R.layout.costumdialog, null);
            builder.setView(convertView2);
            ListView lv = (ListView)convertView2.findViewById(R.id.customListView);
            ArrayAdapter<String> adapter = new ArrayAdapter<String>(ChatActivity.this, R.layout.costumdialog, names)
                    {
                        @Override
                        public View getView(int position, View convertView, ViewGroup parent) 
                        {
                            View row;

                            if (null == convertView) {
                            row = inflater.inflate(R.layout.costumdialog, null);
                            } else {
                            row = convertView;
                            }

                            TextView tv = (TextView)row.findViewById(R.id.singlerow);
                            tv.setText(Html.fromHtml(getItem(position)));
                            //tv.setText(getItem(position));

                            return row;
                        }

                    };
                    lv.setAdapter(adapter);
            AlertDialog alert = builder.create();
            alert.show();

問題是， setAdapter()強制應用程序崩潰，並出現NullPointerException

xml文件等全部存在，我認為它們沒有問題。

誰能幫我？

編輯： 

    06-12 07:26:45.537: E/AndroidRuntime(28036): FATAL EXCEPTION: main
06-12 07:26:45.537: E/AndroidRuntime(28036): java.lang.NullPointerException
06-12 07:26:45.537: E/AndroidRuntime(28036):    at com.flipflopdev.epvp_aj1987_chat.ChatActivity$1$1.getView(ChatActivity.java:82)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.AbsListView.obtainView(AbsListView.java:2075)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.ListView.measureHeightOfChildren(ListView.java:1476)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.ListView.onMeasure(ListView.java:1339)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.View.measure(View.java:12948)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5005)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.View.measure(View.java:12948)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5005)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.View.measure(View.java:12948)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5005)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1369)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:660)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:553)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.View.measure(View.java:12948)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5005)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.View.measure(View.java:12948)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5005)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.View.measure(View.java:12948)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5005)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:293)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2141)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.View.measure(View.java:12948)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1206)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.view.ViewRootImpl.handleMessage(ViewRootImpl.java:2666)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.os.Handler.dispatchMessage(Handler.java:99)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.os.Looper.loop(Looper.java:156)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at android.app.ActivityThread.main(ActivityThread.java:4977)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at java.lang.reflect.Method.invokeNative(Native Method)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at java.lang.reflect.Method.invoke(Method.java:511)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
06-12 07:26:45.537: E/AndroidRuntime(28036):    at dalvik.system.NativeStart.main(Native Method)

R.layout.costumdialog 

    <?xml version="1.0" encoding="utf-8"?>
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/customListView"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >
</ListView>

ChatActivity中的第82行 

tv.setText(Html.fromHtml(getItem(position)));

customtextrow.xml 

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
     >

    <TextView
        android:id="@+id/singlerow"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:paddingLeft="5dp">
    </TextView>

</RelativeLayout>

新代碼： 

AlertDialog.Builder builder = new AlertDialog.Builder(ChatActivity.this);
            builder.setTitle("Onlineliste");

            final LayoutInflater inflater = getLayoutInflater();
            //final View convertView2 = (View) inflater.inflate(R.layout.costumdialog, null);
            //builder.setView(convertView2);
            ArrayAdapter<String> adapter = new ArrayAdapter<String>(ChatActivity.this, R.layout.costumdialog, names)
                    {
                        @Override
                        public View getView(int position, View convertView, ViewGroup parent) 
                        {
                            View row;

                            if (null == convertView) {
                            row = inflater.inflate(R.layout.text, null);
                            } else {
                            row = convertView;
                            }

                            TextView tv = (TextView)row.findViewById(R.id.singlerow);
                            tv.setText(Html.fromHtml(getItem(position)));
                            //tv.setText(getItem(position));

                            return row;
                        }

                    };
                    AlertDialog alert = builder.create();
                    ListView lv = (ListView)alert.findViewById(R.id.customListView);
                    lv.setAdapter(adapter); 


            alert.show();

3 個解決方案

解決方案1
 1 已采納  2014-06-12 06:02:25

您costomdialog.xml沒有一個TextView id為singlerow 。 因此， tv為null，並且當您調用setText時會導致NullPointerException 。

從您的評論看來，單行是具有textview的布局，

所以改變這個 

ArrayAdapter<String> adapter = new ArrayAdapter<String>(ChatActivity.this, R.layout.costumdialog, names)

至 

ArrayAdapter<String> adapter = new ArrayAdapter<String>(ChatActivity.this, R.layout.singlerow, names)

編輯： 

ArrayAdapter<String> adapter = new ArrayAdapter<String>(ChatActivity.this, R.layout.customtextrow.xml, names)

完整的例子 

public class MainActivity extends Activity {

 String names[]={"A","B","C"};
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Onlineliste");

    final LayoutInflater inflater = getLayoutInflater();
    final View convertView2 = (View) inflater.inflate(R.layout.costomdialog, null);
    builder.setView(convertView2);
    ListView lv = (ListView)convertView2.findViewById(R.id.customListView);
    ArrayAdapter<String> adapter = new ArrayAdapter<String>(MainActivity.this, R.layout.costomdialog, names)
            {
                @Override
                public View getView(int position, View convertView, ViewGroup parent) 
                {
                    View row;

                    if (null == convertView) {
                    row = inflater.inflate(R.layout.customtextrow, null);
                    } else {
                    row = convertView;
                    }

                    TextView tv = (TextView)row.findViewById(R.id.singlerow);
                    tv.setText(names[position]);
                    //tv.setText(getItem(position));

                    return row;
                }

            };
            lv.setAdapter(adapter);
    AlertDialog alert = builder.create();
    alert.show();
     }
   }

xml一樣沒有變化

快：

在此處輸入圖片說明

編輯2：

為什么Html.fromHtml不起作用？ ：/見我的名字ArrayList最終的ArrayList名稱= new ArrayList（）;
字符串[]拆分= response.split（“ \\ |”）; for（String name：splitted）{names.add（Html.fromHtml（“” + name.split（“ \\ +”） 1 +“”）.toString（））; }

拆分字符串，將其添加到arraylist。 將文本設置為textview時設置html。

解決方案2
 1  2014-06-12 06:03:26

問題是您正在膨脹R.layout.costumdialog而沒有任何TextView，您不需要在ListView內膨脹ListView，只需將TextView添加到R.layout.costumdialog

創建一個名為text.xml的新布局 

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/singlerow"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="TextView" />

</LinearLayout>

改成這個 

if (null == convertView) {
     row = inflater.inflate(R.layout.text, null);

這不是將適配器設置為ListView的正確方法，您需要從AlertDialog獲取ListView引用以使其能夠使用適配器。

例：

錯誤 

      ListView lv = (ListView)convertView2.findViewById(R.id.customListView);

對 

   AlertDialog alert = builder.create();
   ListView lv = (ListView)alert.findViewById(R.id.customListView);

完整代碼： 

  AlertDialog.Builder builder = new AlertDialog.Builder(ChatActivity.this);
        builder.setTitle("Onlineliste");

        final LayoutInflater inflater = getLayoutInflater();
        final View convertView2 = (View) inflater.inflate(R.layout.costumdialog, null);
        builder.setView(convertView2);

        AlertDialog alert = builder.create();

        ListView lv = (ListView)alert.findViewById(R.id.customListView);
        ArrayAdapter<String> adapter = new ArrayAdapter<String>(ChatActivity.this, R.layout.text, names)
                {
                    @Override
                    public View getView(int position, View convertView, ViewGroup parent) 
                    {
                        View row = super.getView(position, convertView, parent);
                        TextView tv = (TextView)row.findViewById(R.id.singlerow);
                        tv.setText(Html.fromHtml(getItem(position)));
                        //tv.setText(getItem(position));

                        return row;
                    }

                };
        lv.setAdapter(adapter);

        alert.show();

解決方案3
 -1  2014-06-12 05:55:25

我認為問題出在充氣機上， 

final View convertView2 = (View) inflater.inflate(R.layout.costumdialog, null);

您正在投射不必要的視圖。

嘗試這樣的事情 

protected Dialog onCreateDialog() {
        LayoutInflater factory = LayoutInflater.from(this);
        final View textEntryView = factory.inflate(R.layout.alert_dialog_text_entry, null);
        return new AlertDialog.Builder(TicTacToe.this)
            //.setIconAttribute(android.R.attr.alertDialogIcon)
            .setTitle(getTitleText())
            .setView(textEntryView)
            .setPositiveButton("JOIN GAME", new DialogInterface.OnClickListener() {
                public void onClick(DialogInterface dialog, int whichButton) {
                    try
                    {
                        EditText et = (EditText)findViewById(R.id.username_edit);
                            playerName = et.getText().toString();
                    }
                    catch (Exception e)
                    {
                    }
                }
            })
            .create();
    return null;
}

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