android

问题 Tim Bray's article "Saving Data Safely" left me with open questions. Today, it's over a month old and I haven't seen any follow-up on it, so I decided to address the topic here. One point of the article is that FileDescriptor.sync() should be called to be on the safe side when using FileOutputStream. At first, I was very irritated, because I never have seen any Java code doing a sync during the 12 years I do Java. Especially since coping with files is a pretty basic thing. Also, the standard

问题 I've been experimenting with ConstraintLayout, is there a way to set the max width of a view to a percentage of the parent (and a height of match constraint and dimension ratio of 1:1)? Here is the code without using max width: <?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="wrap_content">

问题 I've been experimenting with ConstraintLayout, is there a way to set the max width of a view to a percentage of the parent (and a height of match constraint and dimension ratio of 1:1)? Here is the code without using max width: <?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="wrap_content">

问题 I try to implement a search bar like in google maps android app: When the recycler view is in its initial state, the toolbar has no elevation. Only when the users starts scrolling the elevation becomes visible. And the search bar (toolbar) never collapses. Here is what I tried to replicate this: <android.support.design.widget.CoordinatorLayout android:layout_width="match_parent" android:layout_height="match_parent" android:fitsSystemWindows="true"> <android.support.v7.widget.RecyclerView

问题 What is the benefit of using Retrofit in combination with Rxjava? 回答1: Question Retrofit Already in run on background thread. Then why need another background task RxJava? I think most importanly, avoid nested callbacks( callback hell ). e.g) Callback hell (Retrofit) public interface MyService { @GET("users") Call<List<UserModel>> getUser(); @GET("userinfo") Call<UserInfoModel> getUserInfoById(@Query("id") Integer id); } service.getUser().enqueue(new Callback<UserModel>() { @Override public

问题 I want to record human voice on my Android phone. I noticed that Android has two classes to do this: AudioRecord and MediaRecorder. Can someone tell me what's the difference between the two and what are appropriate use cases for each? I want to be able to analyse human speech in real-time to measure amplitude, etc. Am I correct in understanding that AudioRecord is better suited for this task? I noticed on the official Android guide webpage for recording audio, they use MediaRecorder with no

问题 When i run this program, it repeatedly saying that "cannot resolve symbol setOnClickListener".anyone please help me to solve this problem. import android.support.v7.app.AppCompatActivity; import android.content.Intent; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.view.View; import android.view.View.OnClickListener; import android.widget.TextView; public class MainActivity extends AppCompatActivity { @Override protected void onCreate(Bundle

问题 Can anyone tell me what are the different of use of onAttach() and isAdded in Android Fragment? When create a new fragment onAttach() method creating default. I checked this question, the question is asked about !onDetech() and isAdded() , also one answer there, but I am not clear with that.. Thanks 回答1: This could be answered simply reading javadocs: /** * Called when a fragment is first attached to its context. * {@link #onCreate(Bundle)} will be called after this. */ public void onAttach

问题 Can anyone tell me what are the different of use of onAttach() and isAdded in Android Fragment? When create a new fragment onAttach() method creating default. I checked this question, the question is asked about !onDetech() and isAdded() , also one answer there, but I am not clear with that.. Thanks 回答1: This could be answered simply reading javadocs: /** * Called when a fragment is first attached to its context. * {@link #onCreate(Bundle)} will be called after this. */ public void onAttach