刚学习安卓不久，写了一个关于进度条的小程序。功能是点击按钮后出现进度条，且进度条自动前进。不过点击了按钮后进度条出现了，但是按钮也消失了。。
代码：
MainActivity.java:
package com.example.barprogress;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
public class MainActivity extends Activity {
ProgressBar bar = null;
Button myButton = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bar = (ProgressBar)findViewById(R.id.bar);
myButton = (Button)findViewById(R.id.myButton);
myButton.setOnClickListener(new ButtonListener());
}
class ButtonListener implements OnClickListener{
@Override
public void onClick(View arg0) {
bar.setVisibility(View.VISIBLE);
barHandler.post(updateThread);
}
}
Handler barHandler = new Handler(){
public void handleMessage(android.os.Message msg) {
bar.setProgress(msg.arg1);
barHandler.post(updateThread);
}};
Runnable updateThread = new Runnable(){
int i = 0;
public void run(){
i = i+ 10;
System.out.println("Begin Thread");
Message msg = barHandler.obtainMessage();
msg.arg1 = i;
try{
Thread.sleep(1000);
}catch(InterruptedException e){
e.printStackTrace();
}
barHandler.sendMessage(msg);
if(i == 100){
barHandler.removeCallbacks(updateThread);
}
}
};
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
activity_main.xml:
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
tools:context=".MainActivity" >
<ProgressBar
android:id="@+id/bar"
android:layout_width="200dp"
android:layout_height="fill_parent"
style="?android:attr/progressBarStyleHorizontal"
android:visibility="gone"/>
<Button
android:id="@+id/myButton"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="start"/>
</LinearLayout>
刚开始画面：
点击按钮后，按钮消失，进度条位置也不在最上方：
------解决思路----------------------
1.按钮消失是因为进度条的高度是match_parent，所以进度条显示出来的时候就把按钮遮住了。
2.你的进程模型有问题，Handler是在UI线程里创建的，执行barHandler.post(updateThread)使得updateThread会在UI线程里执行，导致updateThread里的sleep把UI线程阻塞了。
我帮你改了一下
public class MainActivity extends Activity {
ProgressBar bar = null;
Button myButton = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bar = (ProgressBar)findViewById(R.id.bar);
myButton = (Button)findViewById(R.id.myButton);
myButton.setOnClickListener(new ButtonListener());
}
class ButtonListener implements OnClickListener {
@Override
public void onClick(View arg0) {
bar.setVisibility(View.VISIBLE);
new Thread(updateThread){}.start();
}
}
Handler barHandler = new Handler() {
public void handleMessage(android.os.Message msg) {
bar.setProgress(msg.arg1);
new Thread(updateThread){}.start();
}
};
Runnable updateThread = new Runnable(){
int i = 0;
public void run(){
if (i < 100) {
i += 10;
System.out.println("Begin Thread");
try{
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Message msg = barHandler.obtainMessage();
msg.arg1 = i;
barHandler.sendMessage(msg);
}
}
};
}
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<Button
android:id="@+id/myButton"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="start"/>
<ProgressBar
android:id="@+id/bar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
style="?android:attr/progressBarStyleHorizontal"
android:visibility="gone"/>
</LinearLayout>
------解决思路----------------------
其实这样效率上不会太高，因为进度条每次更新时都创建一个线程。你可以只创建一个后台线程，在一个loop里做消息处理。
改进以后的程序是这样的：
public class MainActivity extends Activity {
ProgressBar bar = null;
Button myButton = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bar = (ProgressBar)findViewById(R.id.bar);
myButton = (Button)findViewById(R.id.myButton);
myButton.setOnClickListener(new ButtonListener());
}
class ButtonListener implements OnClickListener {
@Override
public void onClick(View arg0) {
bar.setVisibility(View.VISIBLE);
new Thread(updateThread){}.start();
}
}
Handler barHandler = new Handler() {
public void handleMessage(android.os.Message msg) {
bar.setProgress(msg.arg1);
}
};
Runnable updateThread = new Runnable(){
public void run(){
System.out.println("Begin Thread");
for (int i = 0; i <= 100; i += 10) {
try{
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
Message msg = barHandler.obtainMessage();
msg.arg1 = i;
barHandler.sendMessage(msg);
}
}
};
}
------解决思路----------------------
点击编辑窗口上方右数第六个按钮（带有<>标记），从下拉菜单中选择需要的语言，系统会自动在编辑窗口里生成配对的标签，你在标签里粘帖上你的代码就可以了。