Question

我是android开发的新手，正在尝试解决我的应用程序中某些已安装的应用程序的问题。问题是出现一些投射错误

（无法将android.support.constraint.ConstraintLayout强制转换为android.widget.TextView）

我在这里提到过很多帖子，我试图弄清楚，但是没有运气。作为最后的尝试，我将代码发布在这里，希望得到答复。整个代码发布在下面。

任何帮助将不胜感激

ApplicationAdapter.java

package e.nani.myapplication;

            import android.annotation.SuppressLint;
            import android.content.Context;
            import android.content.Intent;
            import android.content.pm.ApplicationInfo;
            import android.content.pm.PackageInfo;
            import android.content.pm.PackageManager;
            import android.content.pm.ResolveInfo;
            import android.graphics.drawable.Drawable;
            import android.support.constraint.ConstraintLayout;
            import android.support.v7.app.AppCompatActivity;
            import android.os.Bundle;
            import android.util.Log;
            import java.util.List;

            import android.view.LayoutInflater;
            import android.view.View;
            import android.view.ViewGroup;
            import android.widget.ArrayAdapter;
            import android.widget.ImageView;
            import android.widget.LinearLayout;
            import android.widget.ListAdapter;
            import android.widget.ListView;
            import android.widget.RelativeLayout;
            import android.widget.TextView;

            import java.util.ArrayList;

            public class ApplicationAdapter extends ArrayAdapter<ApplicationInfo > {

                private int resourceLayout;
                private Context mContext;
                List<ApplicationInfo> items;
                PackageManager pm ;
                ApplicationInfo p;


                public ApplicationAdapter(Context context, int resource, List<ApplicationInfo> items) {
                    super(context, resource, items);
                    this.resourceLayout = resource;
                    this.mContext = context;

                    this.items = items;
                }

                @Override
                public View getView(int position, View convertView, ViewGroup parent) {


                    View view = convertView;
                    if (null == view) {
                        LayoutInflater layoutInflater = (LayoutInflater) mContext
                                .getSystemService(mContext.LAYOUT_INFLATER_SERVICE);
                        view = layoutInflater.inflate(R.layout.row_view, null);
                    }
                    pm=mContext.getPackageManager();

                    p = items.get(position);

                   if (p!= null) {
                        ImageView tt1 = (ImageView)view.findViewById(R.id.img);
                        TextView tt2=  (TextView)view.findViewById(R.id.t1);
                        if (tt1 !=   null) {
                            tt1.setImageDrawable(p.loadIcon(pm));
                        }

                        if (tt2 != null) {
                            tt2.setText(p.packageName);
                        }


                  }

                    return view;

                }
            }

MainActivity.java

                    package e.nani.myapplication;

                import android.annotation.SuppressLint;
                import android.app.ListActivity;
                import android.content.Context;
                import android.content.Intent;
                import android.content.pm.ApplicationInfo;
                import android.content.pm.PackageInfo;
                import android.content.pm.PackageManager;
                import android.content.pm.ResolveInfo;
                import android.graphics.drawable.Drawable;
                import android.support.v7.app.AppCompatActivity;
                import android.os.Bundle;
                import android.util.Log;
                import java.util.List;

                import android.view.LayoutInflater;
                import android.view.View;
                import android.view.ViewGroup;
                import android.widget.ArrayAdapter;
                import android.widget.ImageView;
                import android.widget.ListAdapter;
                import android.widget.ListView;
                import android.widget.TextView;

                import java.util.ArrayList;



                public class MainActivity extends AppCompatActivity {

                    ListView listview;
                    ApplicationAdapter<ApplicationInfo> adapter;
                    List<ApplicationInfo> ls=new ArrayList<>();
                    PackageManager pm;

                    protected void onCreate(Bundle savedInstanceState) {
                        super.onCreate(savedInstanceState);
                        setContentView(R.layout.activity_main);
                        listview = (ListView) findViewById(R.id.lists);
                        try {
                            pm= getPackageManager();

                            List<ApplicationInfo> packages = pm.getInstalledApplications(PackageManager.GET_META_DATA);

                            for (ApplicationInfo packageInfo : packages) {



                                ls.add(packageInfo);
                                adapter = new ApplicationAdapter<ApplicationInfo>(this, R.layout.row_view, ls);
                                listview.setAdapter(adapter);
                                Log.i("added", String.valueOf(pm.getClass().getName()));
                                Log.i("middle",packageInfo.packageName);
                            }
                        } catch (Exception e) {
                            e.printStackTrace();
                        }



                    }


                }

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
                    <android.widget.RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                        xmlns:app="http://schemas.android.com/apk/res-auto"
                        xmlns:tools="http://schemas.android.com/tools"
                        android:layout_width="match_parent"
                        android:layout_height="match_parent"
                        tools:context=".MainActivity">

                        <ListView
                            android:id="@+id/lists"
                            android:layout_width="match_parent"
                            android:layout_height="match_parent"
                            android:layout_alignParentStart="true"
                            android:layout_alignParentTop="true" />
                    </android.widget.RelativeLayout>

row_view.xml

<?xml version="1.0" encoding="utf-8"?>
            <android.support.constraint.ConstraintLayout
                xmlns:android="http://schemas.android.com/apk/res/android"
                xmlns:app="http://schemas.android.com/apk/res-auto"
                android:layout_width="match_parent"
                android:layout_height="match_parent"
                >

                <TextView
                    android:id="@+id/t1"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="TextView" />

                <TextView
                    android:id="@+id/t2"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:text="TextView" />

                <ImageView
                    android:id="@+id/img"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content" />
            </android.support.constraint.ConstraintLayout>

``崩溃报告

 Caused by: java.lang.ClassCastException: android.support.constraint.ConstraintLayout cannot be cast to android.widget.TextView
    at android.widget.ArrayAdapter.createViewFromResource(ArrayAdapter.java:432)
    at android.widget.ArrayAdapter.getView(ArrayAdapter.java:415) 
    at e.nani.myapplication.ApplicationAdapter.getView(ApplicationAdapter.java:49) 
    at android.widget.AbsListView.obtainView(AbsListView.java:2408) 
    at android.widget.ListView.makeAndAddView(ListView.java:2126) 
    at android.widget.ListView.fillDown(ListView.java:851) 
    at android.widget.ListView.fillDown(ListView.java:833) 
    at android.widget.ListView.fillFromTop(ListView.java:921) 
    at android.widget.ListView.layoutChildren(ListView.java:1900) 
    at android.widget.AbsListView.onLayout(AbsListView.java:2207) 
    at android.view.View.layout(View.java:20831) 
    at android.view.ViewGroup.layout(ViewGroup.java:6203) 
    at android.widget.RelativeLayout.onLayout(RelativeLayout.java:1083) 
    at android.view.View.layout(View.java:20831) 
    at android.view.ViewGroup.layout(ViewGroup.java:6203) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at android.view.View.layout(View.java:20831) 
    at android.view.ViewGroup.layout(ViewGroup.java:6203) 
    at android.support.v7.widget.ActionBarOverlayLayout.onLayout(ActionBarOverlayLayout.java:444) 
    at android.view.View.layout(View.java:20831) 
    at android.view.ViewGroup.layout(ViewGroup.java:6203) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at android.view.View.layout(View.java:20831) 
    at android.view.ViewGroup.layout(ViewGroup.java:6203) 
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1812) 
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1656) 
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1565) 
    at android.view.View.layout(View.java:20831) 
    at android.view.ViewGroup.layout(ViewGroup.java:6203) 
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323) 
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261) 
    at com.android.internal.policy.DecorView.onLayout(DecorView.java:754) 
    at android.view.View.layout(View.java:20831) 
    at android.view.ViewGroup.layout(ViewGroup.java:6203) 
    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2991) 
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2504) 
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1635) 
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:7795) 
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:1172) 
    at android.view.Choreographer.doCallbacks(Choreographer.java:984) 
    at android.view.Choreographer.doFrame(Choreographer.java:809) 
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:1158) 
    at android.os.Handler.handleCallback(Handler.java:873) 
    at android.os.Handler.dispatchMessage(Handler.java:99) 
    at android.os.Looper.loop(Looper.java:193) 
    at android.app.ActivityThread.main(ActivityThread.java:6863) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:537) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:858)

Answer 1

尝试使用ViewHolder模式：

static class ViewHolder {
    ImageView tt1;
    TextView tt2;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View view = convertView;
    ViewHolder holder;

    if (null == view) {
        LayoutInflater layoutInflater = (LayoutInflater) mContext.getSystemService(mContext.LAYOUT_INFLATER_SERVICE);
        view = layoutInflater.inflate(R.layout.row_view, null);
        holder = new ViewHolder();
        holder.tt1 = (ImageView)view.findViewById(R.id.img);
        holder.tt2 = (TextView)view.findViewById(R.id.t1);
        view.setTag(holder);
    } else {
        holder = (ViewHolder) view.getTag();
    }

    pm = mContext.getPackageManager();
    p = items.get(position);
    if (p != null) {
        holder.tt1.setImageDrawable(p.loadIcon(pm));
        holder.tt2.setText(p.packageName);
    }

    return view;
}

有用的链接： https://stackoverflow.com/a/3832467/10995239

将约束视图投射到文本视图时发生致命错误

1 个答案: