android 异步任务的一个后台方法本质是开启一个线程完毕耗时操作，其它onPostExecute方法和onPreExecute方法执行在UI主线程用于更新UI界面。为了提高用户体验常见的异步任务载入方式如今总结例如以下：
1、异步载入界面效果例如以下:
关键代码例如以下所看到的：
/**
* 异步任务给列表载入数据
*/
private void fillData(){
new AsyncTask
@Override
protected void onPreExecute() {
loading.setVisibility(View.VISIBLE);
super.onPreExecute();
}
@Override
protected void onPostExecute(Void result) {
loading.setVisibility(View.INVISIBLE);
//刷新界面列表数据
if(mAdapter==null){
mAdapter=new RubishSmsInfosAdapter();
mRubishSms.setAdapter(mAdapter);
}else{
mAdapter.notifyDataSetChanged();
}
super.onPostExecute(result);
}
@Override
protected Void doInBackground(Void... params) {
if(mInfos==null){
mInfos=mRubishSmsInfoDao.findInfosbyPage(maxNum, offset);
}else{
mInfos.addAll(mRubishSmsInfoDao.findInfosbyPage(maxNum, offset));
}
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
}.execute();
}
loading相应的loading=findViewById(R.id.ll_rublish_sms_info_loading);
布局文件例如以下：
activity_rubish_sms.xml
android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > android:layout_width="match_parent" android:layout_height="match_parent" android:layout_weight="100" > android:layout_gravity="center" android:id="@+id/ll_rublish_sms_info_loading" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" android:visibility="invisible" > android:layout_width="match_parent" android:layout_height="wrap_content" /> android:gravity="center" android:layout_width="match_parent" android:layout_height="wrap_content" android:text="数据载入中,请稍后..." android:textSize="13sp" />
android:id="@+id/lv_rubish_sms_content" android:layout_width="match_parent" android:layout_height="wrap_content" > 通过如上代码就可以实现上述效果。 2、利用对话框实现 实现效果图： 异步任务实现 逻辑代码： /** * 扫描病毒 并动态显示在界面 */ private void scanVirus(){ new AsyncTask List String desc=null; Dialog dialog=new Dialog(KillVirusActivity.this); View viewKilling=View.inflate(KillVirusActivity.this,R.layout.killing_dialog,null); @Override protected void onPreExecute() { mKillVirusResult.setText("正在扫描中，请稍等..."); dialog.setCancelable(false); dialog.setContentView(viewKilling); dialog.show(); pm=getPackageManager(); packageInfos=pm.getInstalledPackages(PackageManager.GET_UNINSTALLED_PACKAGES|PackageManager.GET_SIGNATURES); // progressBar.setMax(packageInfos.size()); super.onPreExecute(); } @Override protected void onPostExecute(Void result) { dialog.dismiss(); if(apps.size()>0){ mKillVirusResult.setTextColor(Color.RED); mKillVirusResult.setText("扫描完毕！发现病毒"+apps.size()+"个"+","+"请及时清理"); for(final VirusApp app:apps){ //有病毒 View view=View.inflate(KillVirusActivity.this,R.layout.app_virus_info_item,null); view.setClickable(true); view.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { //卸载程序 Intent intent = new Intent(); intent.setAction("android.intent.action.DELETE"); intent.addCategory(Intent.CATEGORY_DEFAULT); intent.setData(Uri.parse("package:" + app.getmAppVirusName())); startActivity(intent); } }); ImageView appIcon=(ImageView) view.findViewById(R.id.iv_app_icon); TextView appName=(TextView) view.findViewById(R.id.tv_app_name); TextView appDesc=(TextView)view.findViewById(R.id.tv_app_virus_desc); appIcon.setBackground(app.getmAppVirusIcon()); appName.setText(app.getmAppVirusName()); appDesc.setText(app.getmAPPVirusDesc()); mContainer.addView(view); } }else if(apps.size()==0){ mKillVirusResult.setText("扫描完毕！恭喜没有发现病毒。"); } super.onPostExecute(result); } @Override protected Void doInBackground(Void... params) { int total=0; //获得数据库操作对象 VirusDao virusDao=new VirusDao(); //获得设备上全部应用的签名 for(PackageInfo info:packageInfos){ total++; Signature[] signature=info.signatures; try { String md5=Md5Util.encode(signature[0].toString()); desc=virusDao.findVirus(md5); Log.i("杀毒MD5<<<", md5); desc=virusDao.findVirus(md5); } catch (Exception e) { // TODO: handle exception } //Log.i("杀毒<<<", (signature[0]).toString()); //签名用MD5编码获得MD5加密后的应用的签名信息 //Log.i("杀毒MD5<<<", md5); //查询本地病毒签名数据库 // desc=virusDao.findVirus(md5); if(desc!=null){//查询到病毒 VirusApp app=new VirusApp(); //获得应用的图标 Drawable drawable=pm.getApplicationIcon(info.applicationInfo); app.setmAppVirusIcon(drawable); //获得应用名 String appName=(String) pm.getApplicationLabel(info.applicationInfo); app.setmAppVirusName(appName); //获得该应用的病毒描写叙述 app.setmAPPVirusDesc(desc); apps.add(app); app=null; //publishProgress(total,app); }else{ Log.i("杀毒MD5<<<","不是病毒"+total); } } //progressBar.setProgress(total); try { Thread.sleep(200); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } }.execute(); } 该逻辑处理相应的activity布局界面： android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > android:layout_width="match_parent" android:layout_height="35dp" android:background="@drawable/ll_title_bg" android:gravity="center" android:text="手机病毒查杀" /> android:id="@+id/tv_kill_virus_result" android:layout_width="match_parent" android:layout_height="125dp" android:gravity="center" android:background="@drawable/ll_title_bg" /> android:layout_width="match_parent" android:layout_height="wrap_content" > android:id="@+id/ll_container" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical" > 该界面有一个线性布局容器，能够实现动态载入数据的效果。 实现自己定义对话框的布局： android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" > android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="center" /> android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:text="病毒扫描中..." android:textSize="15sp" /> 实现动态扫描并载入数据的整个Activity代码: package com.example.yqqmobilesafe; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.util.ArrayList; import java.util.List; import android.app.Activity; import android.app.Dialog; import android.content.Intent; import android.content.pm.PackageInfo; import android.content.pm.PackageManager; import android.content.pm.Signature; import android.graphics.Color; import android.graphics.drawable.Drawable; import android.net.Uri; import android.os.AsyncTask; import android.os.Bundle; import android.util.Log; import android.view.View; import android.view.View.OnClickListener; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.ProgressBar; import android.widget.TextView; import com.example.yqqmobilesafe.db.dao.VirusDao; import com.example.yqqmobilesafe.domain.VirusApp; import com.example.yqqmobilesafe.utils.CopyFileToSystem; import com.example.yqqmobilesafe.utils.Md5Util; //本地病毒查杀 public class KillVirusActivity extends Activity { private LinearLayout mContainer; private TextView mKillVirusResult; private PackageManager pm; private ProgressBar progressBar; private List public KillVirusActivity() { } @Override protected void onCreate(Bundle savedInstanceState) { setContentView(R.layout.activity_kill_virus); mContainer=(LinearLayout) this.findViewById(R.id.ll_container); mKillVirusResult=(TextView) this.findViewById(R.id.tv_kill_virus_result); //progressBar=(ProgressBar) this.findViewById(R.id.pb_scanning_virus); copyVirusDB();//拷贝本地病毒签名到系统文件夹 scanVirus(); super.onCreate(savedInstanceState); } /** * 扫描病毒 并动态显示在界面 */ private void scanVirus(){ new AsyncTask List String desc=null; Dialog dialog=new Dialog(KillVirusActivity.this); View viewKilling=View.inflate(KillVirusActivity.this,R.layout.killing_dialog,null); @Override protected void onPreExecute() { mKillVirusResult.setText("正在扫描中。请稍等..."); dialog.setCancelable(false); dialog.setContentView(viewKilling); dialog.show(); pm=getPackageManager(); packageInfos=pm.getInstalledPackages(PackageManager.GET_UNINSTALLED_PACKAGES|PackageManager.GET_SIGNATURES); // progressBar.setMax(packageInfos.size()); super.onPreExecute(); } @Override protected void onPostExecute(Void result) { dialog.dismiss(); if(apps.size()>0){ mKillVirusResult.setTextColor(Color.RED); mKillVirusResult.setText("扫描完毕！发现病毒"+apps.size()+"个"+","+"请及时清理"); for(final VirusApp app:apps){ //有病毒 View view=View.inflate(KillVirusActivity.this,R.layout.app_virus_info_item,null); view.setClickable(true); view.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { //卸载程序 Intent intent = new Intent(); intent.setAction("android.intent.action.DELETE"); intent.addCategory(Intent.CATEGORY_DEFAULT); intent.setData(Uri.parse("package:" + app.getmAppVirusName())); startActivity(intent); } }); ImageView appIcon=(ImageView) view.findViewById(R.id.iv_app_icon); TextView appName=(TextView) view.findViewById(R.id.tv_app_name); TextView appDesc=(TextView)view.findViewById(R.id.tv_app_virus_desc); appIcon.setBackground(app.getmAppVirusIcon()); appName.setText(app.getmAppVirusName()); appDesc.setText(app.getmAPPVirusDesc()); mContainer.addView(view); } }else if(apps.size()==0){ mKillVirusResult.setText("扫描完毕！恭喜没有发现病毒！"); } super.onPostExecute(result); } @Override protected Void doInBackground(Void... params) { int total=0; //获得数据库操作对象 VirusDao virusDao=new VirusDao(); //获得设备上全部应用的签名 for(PackageInfo info:packageInfos){ total++; Signature[] signature=info.signatures; try { String md5=Md5Util.encode(signature[0].toString()); desc=virusDao.findVirus(md5); Log.i("杀毒MD5<<<", md5); desc=virusDao.findVirus(md5); } catch (Exception e) { // TODO: handle exception } //Log.i("杀毒<<<", (signature[0]).toString()); //签名用MD5编码获得MD5加密后的应用的签名信息 //Log.i("杀毒MD5<<<", md5); //查询本地病毒签名数据库 // desc=virusDao.findVirus(md5); if(desc!=null){//查询到病毒 VirusApp app=new VirusApp(); //获得应用的图标 Drawable drawable=pm.getApplicationIcon(info.applicationInfo); app.setmAppVirusIcon(drawable); //获得应用名 String appName=(String) pm.getApplicationLabel(info.applicationInfo); app.setmAppVirusName(appName); //获得该应用的病毒描写叙述 app.setmAPPVirusDesc(desc); apps.add(app); app=null; //publishProgress(total,app); }else{ Log.i("杀毒MD5<<<","不是病毒"+total); } } //progressBar.setProgress(total); try { Thread.sleep(200); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } }.execute(); } /** * 拷贝本地病毒库数据库到app文件夹 */ private void copyVirusDB(){ new AsyncTask @Override protected Void doInBackground(Void... params) { //获得要复制到目的地的文件 File file=new File(getFilesDir(),"antivirus.db"); if(file.exists()&&file.length()>0){ }else{ //获得文件输入流 InputStream is=null; try { is=getResources().getAssets().open("antivirus.db"); CopyFileToSystem.copyFile(is, file.getAbsolutePath()); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } return null; } }.execute(); } }
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