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我刚刚在我的 android 小部件中添加了一个搜索功能，以搜索用户安装的应用程序列表。我的应用程序安装得很好，但是当我去搜索应用程序强制关闭的东西时，我收到了这个错误：

10-18 10:08:39.404: E/AndroidRuntime(8965): FATAL EXCEPTION: main
10-18 10:08:39.404: E/AndroidRuntime(8965): java.lang.NullPointerException
10-18 10:08:39.404: E/AndroidRuntime(8965):     at com.example.awesomefilebuilderwidget.Drag_and_Drop_App$2.onTextChanged(Drag_and_Drop_App.java:61)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.widget.TextView.sendOnTextChanged(TextView.java:6576)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.widget.TextView.handleTextChanged(TextView.java:6785)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.widget.TextView$ChangeWatcher.onTextChanged(TextView.java:7001)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at     android.text.SpannableStringBuilder.sendTextChange(SpannableStringBuilder.java:889)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.text.SpannableStringBuilder.change(SpannableStringBuilder.java:352)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.text.SpannableStringBuilder.change(SpannableStringBuilder.java:269)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:432)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:409)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.view.inputmethod.BaseInputConnection.replaceText(BaseInputConnection.java:679)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.view.inputmethod.BaseInputConnection.commitText(BaseInputConnection.java:185)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at com.android.internal.widget.EditableInputConnection.commitText(EditableInputConnection.java:120)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at com.android.internal.view.IInputConnectionWrapper.executeMessage(IInputConnectionWrapper.java:332)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at com.android.internal.view.IInputConnectionWrapper$MyHandler.handleMessage(IInputConnectionWrapper.java:86)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.os.Handler.dispatchMessage(Handler.java:99)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.os.Looper.loop(Looper.java:150)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at android.app.ActivityThread.main(ActivityThread.java:4333)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at java.lang.reflect.Method.invokeNative(Native Method)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at java.lang.reflect.Method.invoke(Method.java:507)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
10-18 10:08:39.404: E/AndroidRuntime(8965):     at dalvik.system.NativeStart.main(Native Method)

这是 Drag_and_Drop_App.java：

package com.example.awesomefilebuilderwidget;

import java.util.List;

import android.app.Activity;
import android.content.Intent;
import android.content.pm.ApplicationInfo;
import android.os.Bundle;
import android.text.Editable;
import android.text.TextWatcher;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.AdapterView.OnItemLongClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

public class Drag_and_Drop_App extends Activity {
private ListView mListAppInfo;
// Search EditText
EditText inputSearch;
AppInfoAdapter adapter;


@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    // set layout for the main screen
    setContentView(R.layout.drag_and_drop_app);
    // import buttons
    Button btnLinkToFeedback = (Button) findViewById(R.id.btnLinkToFeedback);

    // Link to Feedback Screen
    btnLinkToFeedback.setOnClickListener(new View.OnClickListener() {

        public void onClick(View view) {
            Intent i = new Intent(getApplicationContext(),
                    Feedback.class);
            startActivity(i);
            finish();
        }
    });
    // create new adapter
    @SuppressWarnings("unchecked")
    AppInfoAdapter adapter = new AppInfoAdapter(this, (List<ApplicationInfo>) Utilities.getInstalledApplication(this), getPackageManager());
    // load list application
   mListAppInfo = (ListView)findViewById(R.id.lvApps);
    // set adapter to list view
    mListAppInfo.setAdapter(adapter);
    // search bar
    inputSearch = (EditText) findViewById(R.id.inputSearch);

    inputSearch.addTextChangedListener(new TextWatcher() {

        @Override
        public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {

            // When user changed the Text
            // Drag_and_Drop_App.this.adapter.getFilter().filter(cs);  
            Drag_and_Drop_App.this.adapter.getFilter().filter(cs);

        }

        @Override
        public void beforeTextChanged(CharSequence arg0, int arg1, int arg2,
                int arg3) {
            // TODO Auto-generated method stub

        }

        @Override
        public void afterTextChanged(Editable arg0) {
            // TODO Auto-generated method stub                          
        }
        });


    // implement event when an item on list view is selected
    mListAppInfo.setOnItemClickListener(new OnItemClickListener() {

        @Override
        public void onItemClick(AdapterView<?> parent, View view, int pos, long id) {
            // get the list adapter
            AppInfoAdapter appInfoAdapter = (AppInfoAdapter)parent.getAdapter();
            // get selected item on the list
            ApplicationInfo appInfo = (ApplicationInfo)appInfoAdapter.getItem(pos);
            // launch the selected application
            Utilities.launchApp(parent.getContext(), getPackageManager(), appInfo.packageName);
        }

    });

    // implement event when an item on list view is selected via long-click for drag and drop
    mListAppInfo.setOnItemLongClickListener(new OnItemLongClickListener(){

        @Override
        public boolean onItemLongClick(AdapterView<?> parent, View view,
                int pos, long id) {
            // TODO Auto-generated method stub
            // get the list adapter
            AppInfoAdapter appInfoAdapter = (AppInfoAdapter)parent.getAdapter();
            // get selected item on the list
            ApplicationInfo appInfo = (ApplicationInfo)appInfoAdapter.getItem(pos);
            // launch the selected application
            Utilities.launchApp(parent.getContext(), getPackageManager(), appInfo.packageName);
            return true;
        }


    });
}
}

这是第 61 行：

Drag_and_Drop_App.this.adapter.getFilter().filter(cs);

我刚刚添加了一个过滤器，所以我可能在某个地方搞砸了：

package com.example.awesomefilebuilderwidget;

import java.util.ArrayList;
import java.util.List;

import android.content.Context;
import android.content.pm.ApplicationInfo;
import android.content.pm.PackageManager;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.Filter;
import android.widget.Filterable;
import android.widget.ImageView;
import android.widget.TextView;

public class AppInfoAdapter extends BaseAdapter implements Filterable {
private Context mContext;
private List<ApplicationInfo> mListAppInfo;
private PackageManager mPackManager;
private List<ApplicationInfo> originalListAppInfo;
private Filter filter;

public AppInfoAdapter(Context c, List<ApplicationInfo> listApp, PackageManager pm) {
    mContext = c;
    this.originalListAppInfo = this.mListAppInfo = listApp;
    mPackManager = pm;
    }

@Override
public int getCount() {
    return mListAppInfo.size();
}

@Override
public Object getItem(int position) {
    return mListAppInfo.get(position);
}

@Override
public long getItemId(int position) {
    return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    // get the selected entry
    ApplicationInfo entry = (ApplicationInfo) mListAppInfo.get(position);

    // reference to convertView
    View v = convertView;

    // inflate new layout if null
    if(v == null) {
        LayoutInflater inflater = LayoutInflater.from(mContext);
        v = inflater.inflate(R.layout.layout_appinfo, null);
    }

    // load controls from layout resources
    ImageView ivAppIcon = (ImageView)v.findViewById(R.id.ivIcon);
    TextView tvAppName = (TextView)v.findViewById(R.id.tvName);
    TextView tvPkgName = (TextView)v.findViewById(R.id.tvPack);

    // set data to display
    ivAppIcon.setImageDrawable(entry.loadIcon(mPackManager));
    tvAppName.setText(entry.loadLabel(mPackManager));
    tvPkgName.setText(entry.packageName);

    // return view
    return v;
}
@Override
public Filter getFilter() {
    if(filter == null) {
        filter = new Filter() {
            @Override
            protected FilterResults performFiltering(CharSequence constraint) {
                FilterResults results = new FilterResults();
                List<ApplicationInfo> myFilteredAppList = new ArrayList<ApplicationInfo>();
                constraint = constraint.toString().toLowerCase();

                for (ApplicationInfo appInfo : originalListAppInfo) {
                    String somefield = appInfo.name;
                    if (somefield.toLowerCase().contains(constraint.toString())) {
                        myFilteredAppList.add(appInfo);
                    }
                }
                results.count = myFilteredAppList.size();
                results.values = myFilteredAppList;
                return results;
            }

            @SuppressWarnings("unchecked")
            @Override
            protected void publishResults(CharSequence constraint, FilterResults results) {
                mListAppInfo = (List<ApplicationInfo>)results.values;
                notifyDataSetChanged();
            }
        };
    }
    return filter;
}

}

我担心的一行是我的过滤器中的这一行：

                        String somefield = appInfo.name;
                    if (somefield.toLowerCase().contains(constraint.toString())) {

我不确定应该在 appInfo 中过滤哪个字段。如果有帮助，这里是我的 xml 布局（片段）：

                <!-- Editext for Search -->
<EditText android:id="@+id/inputSearch"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:hint="@string/Search_applications"
    android:inputType="textVisiblePassword"/>

<ListView
    android:id="@+id/lvApps"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"

有什么问题？

添加： 在此处输入图像描述

4

2 回答 2

1

您已经将 AppInfoAdapter 声明为成员变量。在 oncreate 里面应该是：

adapter = new AppInfoAdapter(this, (List<ApplicationInfo>)   Utilities.getInstalledApplication(this), getPackageManager());

不是

AppInfoAdapter  adapter = new AppInfoAdapter(this, (List<ApplicationInfo>)   Utilities.getInstalledApplication(this), getPackageManager());
于 2013-10-18T16:53:16.597 回答
1

我完全同意 Mikel 的评论，您的代码中有很多嵌套调用，这使得 1. 难以阅读和 2. 难以调试。

我还没有机会测试，但我想知道电话Drag_and_Drop_App.this.adapter是否返回空值。如果要测试 null 的来源，请编写如下快速测试：

public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
    // When user changed the Text
    // Drag_and_Drop_App.this.adapter.getFilter().filter(cs);  
     if (Drag_and_Drop_App.this.adapter == null){
         // some print statement saying it is null
     }
        Drag_and_Drop_App.this.adapter.getFilter().filter(cs);

    }

我以某种方式怀疑您没有正确声明适配器。你还没有声明它是静态的，但你试图这样称呼它。拥有一大堆全局静态变量并不是最佳实践，相反，您应该更倾向于编写“getter”和“setter”方法，例如

public void setAdapter(AppInfoAdapter adapter){
    this.adapter = adapter;
}

public AppInfoAdapter getAdapter(){
    return this.adapter
}

但是尝试正确声明适配器，看看是否能解决眼前的问题。

编辑：

就像我说的，虽然这不是最佳实践，但看看将适配器声明为静态是否至少能让你走得更远。

public static AppInfoAdapter adapter;
于 2013-10-18T16:34:46.253 回答