Question

我正在制作显示应用程序列表的应用程序这是我的代码：-

MainActivity.java

import android.app.*;
import android.content.*;
import android.content.pm.*;
import android.os.*;
import android.view.*;
import android.widget.*;
import java.util.*;
import android.graphics.drawable.*;
import android.content.pm.PackageManager.*;

public class MainActivity extends Activity 
{
    ProgressDialog pd;
    List<Drawable> ld;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    pd = new ProgressDialog(this);
    pd.setTitle("Loading...");
    pd.setCancelable(true);
    pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    pd.create();
    pd.show();
    }

    @Override
    protected void onResume()
    {
    super.onResume();
    createlist();
    }


    public void createlist(){
    ld=new ArrayList<Drawable>();
    List<String> pl= new ArrayList<String>();
    PackageManager pm= getPackageManager();
    List<ApplicationInfo> l = pm.getInstalledApplications(PackageManager.GET_META_DATA);
    for(ApplicationInfo ai:l){
        String name= ai.packageName.toString();
        pl.add(name);
        try
        {
        Drawable d = getApplicationContext().getPackageManager().getApplicationIcon(name);
        ld.add(d);
        }
        catch (PackageManager.NameNotFoundException e)
        {}
    }
    ListView lv = (ListView) findViewById(R.id.mainListView1);
    ArrayAdapter aa= new MyAda(this,pl);
        lv.setAdapter(aa);
//pd.dismiss();
        }

    class MyAda extends ArrayAdapter{
    public MyAda(Context c,List val){
        super(c,R.layout.list,val);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        LayoutInflater li= LayoutInflater.from(getApplicationContext());
        View view = li.inflate(R.layout.list,null);
        TextView tv = (TextView) view.findViewById(R.id.listTextView1);
        tv.setText(getItem(position).toString());
        ImageView iv = (ImageView) view.findViewById(R.id.listImageView1);
        iv.setImageDrawable(ld.get(position));
        return view;
    }

    }
}

当应用程序列表完全加载时，我的应用程序显示进度对话框，但是我想在加载应用程序列表时显示进度对话框这需要更多时间才能启动应用

请告诉我在列表加载数据时显示进度对话框的正确方法

Answer 1

移动创建列表函数以分隔线程，您可以为此使用异步任务，在onPreExecute中显示前移对话框，然后在onPost execute中关闭它。

将以下代码粘贴到您的活动中，它应该可以正常工作。

ProgressDialog pd;
List<Drawable> ld;
List<String> pl;
@Override
protected void onCreate(Bundle savedInstanceState)
{
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main3);
    pd = new ProgressDialog(this);
    pd.setTitle("Loading...");
    pd.setCancelable(true);
    pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    pd.create();


}

@Override
protected void onResume()
{
    super.onResume();
    new AsyncTask<Void,Void,Void>(){

        @Override
        protected void onPreExecute() {
            super.onPreExecute();
            pd.show();
        }

        @Override
        protected Void doInBackground(Void... voids) {
            createlist();
            return null;
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            super.onPostExecute(aVoid);
            pd.dismiss();
            ListView lv = (ListView) findViewById(R.id.listView);
            ArrayAdapter aa= new MyAda(Main3Activity.this,pl);
            lv.setAdapter(aa);
        }
    }.execute();


}


public void createlist(){
    ld=new ArrayList<Drawable>();
    pl= new ArrayList<String>();
    PackageManager pm= getPackageManager();
    List<ApplicationInfo> l = pm.getInstalledApplications(PackageManager.GET_META_DATA);
    for(ApplicationInfo ai:l){
        String name= ai.packageName.toString();
        pl.add(name);
        try
        {
            Drawable d = getApplicationContext().getPackageManager().getApplicationIcon(name);
            ld.add(d);
        }
        catch (PackageManager.NameNotFoundException e)
        {}
    }



}

class MyAda extends ArrayAdapter{
    public MyAda(Context c, List val){
        super(c,R.layout.list,val);
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent)
    {
        LayoutInflater li= LayoutInflater.from(getApplicationContext());
        View view = li.inflate(R.layout.list,null);
        TextView tv = (TextView) view.findViewById(R.id.txt);
        tv.setText(getItem(position).toString());
        ImageView iv = (ImageView) view.findViewById(R.id.iv);
        iv.setImageDrawable(ld.get(position));
        return view;
    }

}

您没有在代码中看到进度对话框，因为您正在主线程中显示进度对话框和获取应用程序数据，主线程一次只能做一件事。将繁重的工作移至后台线程始终是一个好习惯，以实现流畅的UI和性能优势。另外，异步任务不是执行多线程的bset方法，请参考https://medium.com/@maheswaranapk/android-threading-introduction-90e91e196600

Answer 2

尝试将createlist();移到pd.show();下方并删除onResume

Answer 3

'将进度对话框代码添加到诸如此类的createlist（）函数中

 public void createlist(){

 pd = new ProgressDialog(this);
    pd.setTitle("Loading...");
    pd.setCancelable(true);
    pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);
    pd.create();
    pd.show();

    ld=new ArrayList<Drawable>();
    List<String> pl= new ArrayList<String>();
    PackageManager pm= getPackageManager();
    List<ApplicationInfo> l = pm.getInstalledApplications(PackageManager.GET_META_DATA);
    for(ApplicationInfo ai:l){
        String name= ai.packageName.toString();
        pl.add(name);
        try
        {
        Drawable d = getApplicationContext().getPackageManager().getApplicationIcon(name);
        ld.add(d);
        }
        catch (PackageManager.NameNotFoundException e)
        {}
    }
    ListView lv = (ListView) findViewById(R.id.mainListView1);
    ArrayAdapter aa= new MyAda(this,pl);
        lv.setAdapter(aa);
          pd.dismiss();
        }

“在此功能结束时关闭对话框”

“希望您能得到答案”

在加载列表时显示进度对话框

3 个答案: