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安卓面试集锦
再按一次退出
Handler handler = new Handler(Looper.getMainLooper());
if (isExit) {
handler.removeCallbacks(onBackTimeThread);
isExit = false;
finish();
} else {
isExit = true;
Toast.makeText(this, "再按一下退出", Toast.LENGTH_SHORT).show();
handler.postDelayed(onBackTimeThread, 3000);
}
网络请求
private String requestData(String urlString) {
try {
URL url = new URL(urlString);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(30000);
connection.setRequestMethod("GET"); // GET POST
connection.connect();
int responseCode = connection.getResponseCode();
//String responseMessage = connection.getResponseMessage();
String result = null;
if(responseCode == HttpURLConnection.HTTP_OK){
InputStream inputStream = connection.getInputStream();
Reader reader = new InputStreamReader(inputStream, "UTF-8");
char[] buffer = new char[1024];
reader.read(buffer);
result = new String(buffer);
} else {
}
return result;
} catch (MalformedURLException e) {
e.printStackTrace();
Log.i("myLog","非法的uri");
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
异步任务的简单封装
public interface DataLoader<Result> {
public Result loadData();;
public void updateUi(Result result);
}
public class SimpleAsyncTask<Result> extends AsyncTask<Void,Integer,Result>{
private Context context;
private ProgressDialog mProgressDialog;
private String message;
private DataLoader<Result> loader;
public SimpleAsyncTask(Context context,int msgID,DataLoader<Result> loader){
this.context=context;
message=context.getString(msgID);
this.loader=loader;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
mProgressDialog=new ProgressDialog(context);
mProgressDialog.setMessage(message);
mProgressDialog.show();
}
@Override
protected Result doInBackground(Void... params) {
try{
return loader.loadData();
}catch (Exception e){
mProgressDialog.dismiss();
}
return null;
}
@Override
protected void onPostExecute(Result result) {
loader.updateUi(result);
mProgressDialog.dismiss();
super.onPostExecute(result);
}
}
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
public class MusicService extends Service {
public static final String TAG = MusicService.class.getSimpleName();
private MediaPlayer mMediaPlayer;
private MyBinder mMyBinder = new MyBinder();
@Override
public void onCreate() {
super.onCreate();
mMediaPlayer = MediaPlayer.create(this, R.raw.chuxuezhe);
//通知栏
PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, new Intent(this, ServiceTestActivity.class), 0);
NotificationCompat.Builder mBuilder =
new NotificationCompat.Builder(this)
.setSmallIcon(R.mipmap.ic_launcher)
.setContentTitle("My notification")
.setContentText("Hello World!");
mBuilder.setContentIntent(pendingIntent);
NotificationManager mNotifyMgr =
(NotificationManager) getSystemService(NOTIFICATION_SERVICE);
mNotifyMgr.notify(1, mBuilder.build());
}
@Nullable
@Override
public IBinder onBind(Intent intent) {
mMediaPlayer.start();
return mMyBinder;
}
@Override
public int onStartCommand(Intent intent, int flags, int startId) {
mMediaPlayer.start();
return START_NOT_STICKY;
}
@Override
public boolean onUnbind(Intent intent) {
return super.onUnbind(intent);
}
@Override
public void onDestroy() {
super.onDestroy();
mMediaPlayer.stop();
stopForeground(true);
}
public class MyBinder extends Binder {
public MusicService getService() {
return MusicService.this;
}
}
}
public class ServiceTestActivity extends AppCompatActivity implements View.OnClickListener{
private Button start_service,stop_service;
private boolean isBind = false ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_service_test);
start_service= (Button) findViewById(R.id.start_service);
stop_service= (Button) findViewById(R.id.stop_service);
start_service.setOnClickListener(this);
stop_service.setOnClickListener(this);
}
private ServiceConnection mServiceConnection=new ServiceConnection() {
private MusicService mMusicService;
@Override
public void onServiceConnected(ComponentName componentName, IBinder iBinder) {
MusicService.MyBinder binder= (MusicService.MyBinder) iBinder;
mMusicService = binder.getService();
}
@Override
public void onServiceDisconnected(ComponentName componentName) {
mMusicService=null;
}
};
@Override
public void onClick(View view) {
switch (view.getId()){
case R.id.start_service:
isBind =bindService(new Intent(ServiceTestActivity.this, MusicService.class),mServiceConnection,BIND_AUTO_CREATE);
//startService(new Intent(ServiceTestActivity.this, MusicService.class));
break;
case R.id.stop_service:
if (isBind) {
unbindService(mServiceConnection);
isBind = false;
}
//stopService(new Intent(ServiceTestActivity.this, MusicService.class));
break;
}
}
@Override
protected void onDestroy() {
super.onDestroy();
if (isBind) {
unbindService(mServiceConnection);
isBind = false;
}
}
}
广播
public class TestBroadcastReceiver extends BroadcastReceiver {
public static final String TAG = "myLog";
@Override
public void onReceive(Context context, Intent intent) {
if(intent!=null){
if(TextUtils.equals(intent.getAction(), SendBroadcastActivity.COM_XHB_ONLYSTAR)){
Log.i(TAG, "onReceive:action "+intent.getAction());
Log.i(TAG, "onReceive:broadcast "+intent.getStringExtra("toast"));
}
}
}
}
public class SendBroadcastActivity extends AppCompatActivity {
public static final String COM_XHB_ONLYSTAR = "com.xhb.onlystar";
private TestBroadcastReceiver mReceiver;
private IntentFilter mFilter;
private Button mSend;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_send_broadcast);
//注册需要一个IntentFilter
mFilter = new IntentFilter();
mFilter.addAction(COM_XHB_ONLYSTAR);
//注册需要一个广播接收器
mReceiver = new TestBroadcastReceiver();
mSend = (Button) findViewById(R.id.send);
mSend.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent intent=new Intent();
intent.setAction(COM_XHB_ONLYSTAR);
intent.putExtra("toast","this is the broadcast");
sendBroadcast(intent);//发送多个广播能全部接收到
//sendOrderedBroadcast(intent);//按照优先级接收
// LocalBroadcastManager
}
});
}
@Override
protected void onStart() {
super.onStart();
//注册
registerReceiver(mReceiver, mFilter);
}
@Override
protected void onStop() {
super.onStop();
//取消注册
unregisterReceiver(mReceiver);
}
}
底部导航栏的实现
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical">
<FrameLayout
android:id="@+id/realtabcontent"
android:layout_width="fill_parent"
android:layout_height="0dip"
android:layout_weight="1"
android:background="@color/gray" />
<android.support.v4.app.FragmentTabHost
android:id="@android:id/tabhost"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:background="@color/white"/>
</LinearLayout>
public class TestTabHostActivity extends AppCompatActivity {
private FragmentTabHost mTabhost;
private List<Tab> mTabs = new ArrayList<Tab>(5);
private LayoutInflater mInflater;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_test_tab_host);
initView();
}
private void initView() {
Tab tab_home = new Tab(HomeFragment.class, R.string.home, R.drawable.selector_icon_home);
Tab tab_hot = new Tab(HomeFragment.class, R.string.hot, R.drawable.selector_icon_hot);
Tab tab_category = new Tab(HomeFragment.class, R.string.catagory, R.drawable.selector_icon_category);
Tab tab_cart = new Tab(HomeFragment.class, R.string.cart, R.drawable.selector_icon_cart);
Tab tab_mine = new Tab(HomeFragment.class, R.string.mine, R.drawable.selector_icon_mine);
mTabs.add(tab_home);
mTabs.add(tab_hot);
mTabs.add(tab_category);
mTabs.add(tab_cart);
mTabs.add(tab_mine);
mInflater = LayoutInflater.from(this);
mTabhost = (FragmentTabHost) findViewById(android.R.id.tabhost);
mTabhost.setup(this, getSupportFragmentManager(), R.id.realtabcontent);//必须要
for (Tab tab : mTabs) {
TabHost.TabSpec tabSpec = mTabhost.newTabSpec(getString(tab.getTitle()));
tabSpec.setIndicator(buildIndicator(tab));
mTabhost.addTab(tabSpec, tab.getFragment(), null);
}
mTabhost.getTabWidget().setShowDividers(LinearLayout.SHOW_DIVIDER_NONE);//取消item之间的分割线
mTabhost.setCurrentTab(0);//默认选择第一个
}
//得到indicator
private View buildIndicator(Tab tab) {
View view = mInflater.inflate(R.layout.tab_indicator, null);
ImageView img = (ImageView) view.findViewById(R.id.icon_tab);
TextView text = (TextView) view.findViewById(R.id.txt_indicator);
img.setBackgroundResource(tab.getIcon());
text.setText(tab.getTitle());
return view;
}
}
来自为知笔记(Wiz)
安卓面试集锦
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