安卓面试集锦

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  • 再按一次退出

  1.      Handler handler = new Handler(Looper.getMainLooper());
  2.         if (isExit) {
  3.             handler.removeCallbacks(onBackTimeThread);
  4.             isExit = false;
  5.             finish();
  6.         } else {
  7.             isExit = true;
  8.             Toast.makeText(this, "再按一下退出", Toast.LENGTH_SHORT).show();
  9.             handler.postDelayed(onBackTimeThread, 3000);
  10.         }

  • 网络请求

  1.     private String requestData(String urlString) {
  2.         try {
  3.             URL url = new URL(urlString);
  4.             HttpURLConnection connection = (HttpURLConnection) url.openConnection();
  5.             connection.setConnectTimeout(30000);
  6.             connection.setRequestMethod("GET");  // GET POST
  7.             connection.connect();
  8.             int responseCode = connection.getResponseCode();
  9.             //String responseMessage = connection.getResponseMessage();
  10.             String result = null;
  11.             if(responseCode == HttpURLConnection.HTTP_OK){
  12.                 InputStream inputStream = connection.getInputStream();
  13.                 Reader reader = new InputStreamReader(inputStream, "UTF-8");
  14.                 char[] buffer = new char[1024];
  15.                 reader.read(buffer);
  16.                 result = new String(buffer);
  17.             } else {
  19.             }
  20.             return result;
  21.         } catch (MalformedURLException e) {
  22.             e.printStackTrace();
  23.             Log.i("myLog","非法的uri");
  24.         } catch (IOException e) {
  25.             e.printStackTrace();
  26.         }
  27.         return null;
  28.     }

  • 异步任务的简单封装

  1. public interface DataLoader<Result> {
  2.     public Result loadData();;
  3.     public void updateUi(Result result);
  4. }
  1. public class SimpleAsyncTask<Result> extends AsyncTask<Void,Integer,Result>{
  3.     private Context context;
  4.     private ProgressDialog mProgressDialog;
  5.     private String message;
  6.     private DataLoader<Result> loader;
  8.     public SimpleAsyncTask(Context context,int msgID,DataLoader<Result> loader){
  9.         this.context=context;
  10.         message=context.getString(msgID);
  11.         this.loader=loader;
  12.     }
  15.     @Override
  16.     protected void onPreExecute() {
  17.         super.onPreExecute();
  18.         mProgressDialog=new ProgressDialog(context);
  19.         mProgressDialog.setMessage(message);
  20.         mProgressDialog.show();
  21.     }
  23.     @Override
  24.     protected Result doInBackground(Void... params) {
  25.         try{
  26.             return loader.loadData();
  27.         }catch (Exception e){
  28.             mProgressDialog.dismiss();
  29.         }
  30.         return null;
  31.     }
  33.     @Override
  34.     protected void onPostExecute(Result result) {
  35.         loader.updateUi(result);
  36.         mProgressDialog.dismiss();
  37.         super.onPostExecute(result);
  38.     }
  39. }

  • 服务

    Service生命周期的两种方式
  • 1.context.startService() -> onCreate() -> onStartCommand() -> Service running ->context.stopService() -> onDestroy() -> Service stop
  • 2.bindService() ——> onCreate() ——> onBind() ——> Service running ——>
    onUnbind() ——> onDestroy() ——> Service stop
  1. public class MusicService extends Service {
  2.     public static final String TAG = MusicService.class.getSimpleName();
  3.     private MediaPlayer mMediaPlayer;
  4.     private MyBinder mMyBinder = new MyBinder();
  6.     @Override
  7.     public void onCreate() {
  8.         super.onCreate();
  9.         mMediaPlayer = MediaPlayer.create(this, R.raw.chuxuezhe);
  11.         //通知栏
  12.         PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this, ServiceTestActivity.class), 0);
  13.         NotificationCompat.Builder mBuilder =
  14.                 new NotificationCompat.Builder(this)
  15.                         .setSmallIcon(R.mipmap.ic_launcher)
  16.                         .setContentTitle("My notification")
  17.                         .setContentText("Hello World!");
  18.         mBuilder.setContentIntent(pendingIntent);
  19.         NotificationManager mNotifyMgr =
  20.                 (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
  21.         mNotifyMgr.notify(1, mBuilder.build());
  22.     }
  24.     @Nullable
  25.     @Override
  26.     public IBinder onBind(Intent intent) {
  27.         mMediaPlayer.start();
  28.         return mMyBinder;
  29.     }
  31.     @Override
  32.     public int onStartCommand(Intent intent, int flags, int startId) {
  33.         mMediaPlayer.start();
  34.         return START_NOT_STICKY;
  35.     }
  37.     @Override
  38.     public boolean onUnbind(Intent intent) {
  39.         return super.onUnbind(intent);
  40.     }
  42.     @Override
  43.     public void onDestroy() {
  44.         super.onDestroy();
  45.         mMediaPlayer.stop();
  46.         stopForeground(true);
  47.     }
  50.     public class MyBinder extends Binder {
  51.         public MusicService getService() {
  52.             return MusicService.this;
  53.         }
  54.     }
  56. }
  1. public class ServiceTestActivity extends AppCompatActivity implements View.OnClickListener{
  3.     private Button start_service,stop_service;
  4.     private boolean isBind = false ;
  6.     @Override
  7.     protected void onCreate(Bundle savedInstanceState) {
  8.         super.onCreate(savedInstanceState);
  9.         setContentView(R.layout.activity_service_test);
  10.         start_service= (Button) findViewById(R.id.start_service);
  11.         stop_service= (Button) findViewById(R.id.stop_service);
  12.         start_service.setOnClickListener(this);
  13.         stop_service.setOnClickListener(this);
  14.     }
  16.     private ServiceConnection mServiceConnection=new ServiceConnection() {
  17.         private MusicService mMusicService;
  18.         @Override
  19.         public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
  20.             MusicService.MyBinder binder= (MusicService.MyBinder) iBinder;
  21.             mMusicService = binder.getService();
  22.         }
  24.         @Override
  25.         public void onServiceDisconnected(ComponentName componentName) {
  26.             mMusicService=null;
  27.         }
  28.     };
  30.     @Override
  31.     public void onClick(View view) {
  32.         switch (view.getId()){
  33.             case R.id.start_service:
  34.                 isBind =bindService(new Intent(ServiceTestActivity.this, MusicService.class),mServiceConnection,BIND_AUTO_CREATE);
  35.                 //startService(new Intent(ServiceTestActivity.this, MusicService.class));
  36.                 break;
  37.             case R.id.stop_service:
  38.                 if (isBind) {
  39.                     unbindService(mServiceConnection);
  40.                     isBind = false;
  41.                 }
  42.                 //stopService(new Intent(ServiceTestActivity.this, MusicService.class));
  43.                 break;
  44.         }
  45.     }
  47.     @Override
  48.     protected void onDestroy() {
  49.         super.onDestroy();
  50.         if (isBind) {
  51.             unbindService(mServiceConnection);
  52.             isBind = false;
  53.         }
  54.     }
  55. }

  • 广播

  1. public class TestBroadcastReceiver extends BroadcastReceiver {
  2.     public static final String TAG = "myLog";
  3.     @Override
  4.     public void onReceive(Context context, Intent intent) {
  5.         if(intent!=null){
  6.             if(TextUtils.equals(intent.getAction(), SendBroadcastActivity.COM_XHB_ONLYSTAR)){
  7.                 Log.i(TAG, "onReceive:action "+intent.getAction());
  8.                 Log.i(TAG, "onReceive:broadcast "+intent.getStringExtra("toast"));
  9.             }
  10.         }
  11.     }
  12. }
  1. public class SendBroadcastActivity extends AppCompatActivity {
  3.     public static final String COM_XHB_ONLYSTAR = "com.xhb.onlystar";
  4.     private TestBroadcastReceiver mReceiver;
  5.     private IntentFilter mFilter;
  6.     private Button mSend;
  8.     @Override
  9.     protected void onCreate(Bundle savedInstanceState) {
  10.         super.onCreate(savedInstanceState);
  11.         setContentView(R.layout.activity_send_broadcast);
  12.         //注册需要一个IntentFilter
  13.         mFilter = new IntentFilter();
  14.         mFilter.addAction(COM_XHB_ONLYSTAR);
  15.         //注册需要一个广播接收器
  16.         mReceiver = new TestBroadcastReceiver();
  18.         mSend = (Button) findViewById(R.id.send);
  19.         mSend.setOnClickListener(new View.OnClickListener() {
  20.             @Override
  21.             public void onClick(View view) {
  22.                 Intent intent=new Intent();
  23.                 intent.setAction(COM_XHB_ONLYSTAR);
  24.                 intent.putExtra("toast","this is the broadcast");
  25.                 sendBroadcast(intent);//发送多个广播能全部接收到
  26.                 //sendOrderedBroadcast(intent);//按照优先级接收
  27.                // LocalBroadcastManager
  28.             }
  29.         });
  30.     }
  32.     @Override
  33.     protected void onStart() {
  34.         super.onStart();
  35.         //注册
  36.         registerReceiver(mReceiver, mFilter);
  37.     }
  39.     @Override
  40.     protected void onStop() {
  41.         super.onStop();
  42.         //取消注册
  43.         unregisterReceiver(mReceiver);
  44.     }
  45. }

  • 底部导航栏的实现

  1. <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  2.               xmlns:tools="http://schemas.android.com/tools"
  3.               android:layout_width="match_parent"
  4.               android:layout_height="match_parent"
  5.               android:orientation="vertical">
  7.     <FrameLayout
  8.         android:id="@+id/realtabcontent"
  9.         android:layout_width="fill_parent"
  10.         android:layout_height="0dip"
  11.         android:layout_weight="1"
  12.         android:background="@color/gray" />
  14.     <android.support.v4.app.FragmentTabHost
  15.         android:id="@android:id/tabhost"
  16.         android:layout_width="fill_parent"
  17.         android:layout_height="wrap_content"
  18.         android:background="@color/white"/>
  20. </LinearLayout>
  1. public class TestTabHostActivity extends AppCompatActivity {
  3.     private FragmentTabHost mTabhost;
  4.     private List<Tab> mTabs = new ArrayList<Tab>(5);
  5.     private LayoutInflater mInflater;
  7.     @Override
  8.     protected void onCreate(Bundle savedInstanceState) {
  9.         super.onCreate(savedInstanceState);
  10.         setContentView(R.layout.activity_test_tab_host);
  11.         initView();
  12.     }
  14.     private void initView() {
  15.         Tab tab_home = new Tab(HomeFragment.class, R.string.home, R.drawable.selector_icon_home);
  16.         Tab tab_hot = new Tab(HomeFragment.class, R.string.hot, R.drawable.selector_icon_hot);
  17.         Tab tab_category = new Tab(HomeFragment.class, R.string.catagory, R.drawable.selector_icon_category);
  18.         Tab tab_cart = new Tab(HomeFragment.class, R.string.cart, R.drawable.selector_icon_cart);
  19.         Tab tab_mine = new Tab(HomeFragment.class, R.string.mine, R.drawable.selector_icon_mine);
  21.         mTabs.add(tab_home);
  22.         mTabs.add(tab_hot);
  23.         mTabs.add(tab_category);
  24.         mTabs.add(tab_cart);
  25.         mTabs.add(tab_mine);
  27.         mInflater = LayoutInflater.from(this);
  28.         mTabhost = (FragmentTabHost) findViewById(android.R.id.tabhost);
  29.         mTabhost.setup(this, getSupportFragmentManager(), R.id.realtabcontent);//必须要
  31.         for (Tab tab : mTabs) {
  32.             TabHost.TabSpec tabSpec = mTabhost.newTabSpec(getString(tab.getTitle()));
  33.             tabSpec.setIndicator(buildIndicator(tab));
  34.             mTabhost.addTab(tabSpec, tab.getFragment(), null);
  35.         }
  36.         mTabhost.getTabWidget().setShowDividers(LinearLayout.SHOW_DIVIDER_NONE);//取消item之间的分割线
  37.         mTabhost.setCurrentTab(0);//默认选择第一个
  38.     }
  40.     //得到indicator
  41.     private View buildIndicator(Tab tab) {
  42.         View view = mInflater.inflate(R.layout.tab_indicator, null);
  43.         ImageView img = (ImageView) view.findViewById(R.id.icon_tab);
  44.         TextView text = (TextView) view.findViewById(R.id.txt_indicator);
  45.         img.setBackgroundResource(tab.getIcon());
  46.         text.setText(tab.getTitle());
  47.         return view;
  48.     }
  49. }




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