Friday, June 23, 2017

Question of using ContentLoadingProgressBar

android.support.v4.widget.ContentLoadingProgressBar is subclass of ProgressBar. That waits a minimum time to be dismissed before showing. Once visible, the progress bar will be visible for a minimum amount of time to avoid "flashes" in the UI when an event could take a largely variable time to complete (from none, to a user perceivable amount).

 I TRY to use it in this exercise. To display and hide it by calling its show() and hide() methods. By calling show(), show the progress view after waiting for a minimum delay. If during that time, hide() is called, the view is never made visible.

When long progress run after show(), the ContentLoadingProgressBar shown after a short time.
When short progress run after show(), the ContentLoadingProgressBar will not shown.

But the problem is: once ContentLoadingProgressBar no shown once, it will not be shown again! I don't is it normal behavior, or anything wrong.


Here is my exercise:

MainActivity.java
package com.blogspot.android_er.androidcontentloadingprogressbar;

import android.os.AsyncTask;
import android.os.Bundle;
import android.os.SystemClock;
import android.support.v4.widget.ContentLoadingProgressBar;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ProgressBar;

public class MainActivity extends AppCompatActivity {

    Button btnStartShortProgress, btnStartLongProgress;
    ProgressBar progressBar;
    ContentLoadingProgressBar contentLoadingProgressBar;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnStartShortProgress = (Button)findViewById(R.id.startshortprogress);
        btnStartLongProgress = (Button)findViewById(R.id.startlongprogress);
        progressBar = (ProgressBar)findViewById(R.id.ProgressBar);
        contentLoadingProgressBar =
                (ContentLoadingProgressBar)findViewById(R.id.ContentLoadingProgressBar);

        btnStartShortProgress.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                btnStartShortProgress.setEnabled(false);
                btnStartLongProgress.setEnabled(false);
                MyAsyncTask myAsyncTask = new MyAsyncTask();
                myAsyncTask.execute(3);
            }
        });

        btnStartLongProgress.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                btnStartShortProgress.setEnabled(false);
                btnStartLongProgress.setEnabled(false);
                MyAsyncTask myAsyncTask = new MyAsyncTask();
                myAsyncTask.execute(50);
            }
        });
    }

    public class MyAsyncTask extends AsyncTask<Integer, Integer, Void> {

        @Override
        protected Void doInBackground(Integer... integers) {
            int i = integers[0];

            while(i-- > 0){
                SystemClock.sleep(100);
            }

            return null;
        }

        @Override
        protected void onPreExecute() {
            progressBar.setVisibility(View.VISIBLE);
            contentLoadingProgressBar.show();
        }

        @Override
        protected void onPostExecute(Void aVoid) {
            progressBar.setVisibility(View.GONE);
            contentLoadingProgressBar.hide();
            btnStartShortProgress.setEnabled(true);
            btnStartLongProgress.setEnabled(true);
        }
    }
}



activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<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:layout_margin="20dp"
    android:orientation="vertical"
    tools:context="com.blogspot.android_er.androidcontentloadingprogressbar.MainActivity">

    <TextView
        android:id="@+id/title"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:autoLink="web"
        android:text="http://android-er.blogspot.com/"
        android:textStyle="bold"
        />

    <Button
        android:id="@+id/startshortprogress"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Start SHORT Progress"/>
    <Button
        android:id="@+id/startlongprogress"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Start LONG Progress"/>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="ProgressBar"
        android:textStyle="bold"/>
    <ProgressBar
        android:id="@+id/ProgressBar"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="gone"/>

    <TextView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="ContentLoadingProgressBar"
        android:textStyle="bold"/>
    <android.support.v4.widget.ContentLoadingProgressBar
        android:id="@+id/ContentLoadingProgressBar"
        style="?android:attr/progressBarStyle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:visibility="gone"/>
    <ImageView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:src="@mipmap/ic_launcher"/>

</LinearLayout>


Examples of ProgressBar and AsyncTask