Android——Hander和AsyncTask的使用

Handler

倒计时实现方法1（通过线程间的通讯）：

import android.os.Handler;
import android.os.Message;
import java.util.logging.LogRecord;

public class MainActivity extends AppCompatActivity {
private Button mBtnTime;
private int count=60;
private static final int TIME_DESC=0;

private Handler handler=new Handler() {  //Handle注意导对包，android下的包

@Override
public void handleMessage(Message msg){
switch (msg.what){
case TIME_DESC:
String time= (String) msg.obj;
mBtnTime.setText(time);
break;

}
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mBtnTime= (Button) findViewById(R.id.btn_time_desc);
mBtnTime.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
count=60;
new Thread(new Runnable() {
@Override
public void run() {
while (count>0){
count--;
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Message msg=new Message();
msg.obj=count+"秒";
msg.what=TIME_DESC;
handler.sendMessage(msg);
}
}
}).start();

}
});
}

}

倒计时实现方法2

import android.os.Handler;
public class MainActivity extends AppCompatActivity {
private Button mBtnTime;
private int count=60;
private static final int TIME_DESC=0;
private Handler handler=new Handler() {
@Override
public void handleMessage(Message msg){
switch (msg.what){
case TIME_DESC:
if (count>0){
count--;
mBtnTime.setText(count+"秒");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
handler.sendEmptyMessage(TIME_DESC);
break;
}
}}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mBtnTime= (Button) findViewById(R.id.btn_time_desc);
mBtnTime.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
count=60;
handler.sendEmptyMessage(TIME_DESC);
}
});
}
}

AsyncTask

public class MainActivity extends AppCompatActivity {
private Button mBtnStart;
private int count=0;
private ProgressBar mProgressBar;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mProgressBar= (ProgressBar) findViewById(R.id.progressbar);
mBtnStart= (Button) findViewById(R.id.btn_start);
mBtnStart.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
new MyTask().execute("下载完成");//调用MyTask
}
});
}
class MyTask extends AsyncTask<String,String,String>{
@Override
protected void onProgressUpdate(String... values) {
super.onProgressUpdate(values);
int count=Integer.parseInt(values[0]);
mProgressBar.setProgress(count);
}
@Override
protected void onPostExecute(String s) {  //执行完成，s是 doInBadkground的返回值
super.onPostExecute(s);
mBtnStart.setText(s);
}
@Override
protected String doInBackground(String... params) { //后台执行中

while (count<101){
count++;
publishProgress(""+count);//将数据传给onProgressUpdate中values

try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
return params[0];   //返回到onPostExcute中的s
}
}

}