Android移动应用开发之使用异步调用进度条及实现幻灯片切换效果

异步调用进度条

核心代码如下：

package scq.scq.asyntaskdemo;

import androidx.appcompat.app.AppCompatActivity;

import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.SystemClock;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    ProgressDialog pd;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button btnDialog = findViewById(R.id.btn);
        btnDialog.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                showDialog(1);
                new StringTask().execute();
            }
        });
    }
//    创建AsynkTask子类
    private class StringTask extends AsyncTask<Void, Integer, Void>{

        public void printInfo(String info){
            Log.i("asyncTask", info+":Thread is" + Thread.currentThread().getName());
        }
    @Override
    protected Void doInBackground(Void... voids) {
        pd.incrementProgressBy(-pd.getProgress());
        for(int i=0; i<=100; i++){
            publishProgress(i);
            printInfo("doInBackground" + i);
            SystemClock.sleep(50);
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void unused) {
        printInfo("onPostExecute");
        Toast.makeText(getApplicationContext(), "it is over!", Toast.LENGTH_LONG).show();
            super.onPostExecute(unused);
    }

    @Override
    protected void onPreExecute() {
        printInfo("onPreExecute");
        Toast.makeText(getApplicationContext(), "it is begin!", Toast.LENGTH_LONG).show();
            super.onPreExecute();
    }

    @Override
    protected void onProgressUpdate(Integer... values) {
        printInfo("onProgressUpdate");
        pd.incrementProgressBy(1);
        if(values[0] >= 100){
            pd.dismiss();
        }
        super.onProgressUpdate(values);
    }
}

    @Override
    protected Dialog onCreateDialog(int id) {
        pd = new ProgressDialog(this);
        pd.setMax(100);
        pd.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        pd.setTitle("完成进度");
        pd.setMessage("请稍等...");
        pd.setCancelable(false);
        return pd;
    }
}
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示例完整代码

实现幻灯片切换效果

实现思路还是比较简单，就是创建一个线程，然后永真循环，然后根据计数余数确定改呈现什么样的内容。

核心代码如下：

首先线程类：

package scq.scq.handlertest;

public class MyThread extends Thread{
    MainActivity activity;
    int what = 0;
    public MyThread(MainActivity activity){
        this.activity = activity;
    }

    @Override
    public void run() {
        while (true){
            this.activity.handler.sendEmptyMessage((what++)%5);
            try{
                Thread.sleep(300);
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }
}

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因为每次停留300ms然后进行切换。

然后MainActivity中使用Handler根据余数切换内容：

package scq.scq.handlertest;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    TextView tvContent;
    ImageView ivPic;
    Handler handler = new Handler(){
    @Override
    public void handleMessage(@NonNull Message msg) {
        switch (msg.what) {
            case 0:
                tvContent.setText(R.string.andy);
                ivPic.setImageResource(R.drawable.andy);
                break;
            case 1:
                tvContent.setText(R.string.bill);
                ivPic.setImageResource(R.drawable.bill);
                break;
            case 2:
                tvContent.setText(R.string.edgar);
                ivPic.setImageResource(R.drawable.edgar);
                break;
            case 3:
                tvContent.setText(R.string.torvalds);
                ivPic.setImageResource(R.drawable.torvalds);
                break;
            case 4:
                tvContent.setText(R.string.turing);
                ivPic.setImageResource(R.drawable.turing);
                break;
        }
        super.handleMessage(msg);
      }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        this.ivPic = findViewById(R.id.ivPic);
        this.tvContent = findViewById(R.id.tvContent);
        MyThread myThread = new MyThread(this);
        myThread.start();
    }

}
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示例完整代码