我收到错误:android.os.NetworkOnMainThreadException
,我知道解决方法是在 AsnycTask
中运行我的代码。
我不知道如何重构以下代码以使用AsnycTask
?我可以在一个 activity
中完成所有这些吗?
public class MainActivity extends AppCompatActivity {
@Bind(R.id.tvTitle)
TextView title;
@Bind(R.id.etName)
EditText name;
@Bind(R.id.etEmail)
EditText email;
@Bind(R.id.etIdea)
EditText idea;
@Bind(R.id.btnSubmit)
Button submit;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
submit.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
//get input from editText boxes to send to php file on server
String toSubmit = name.getText().toString() + " " + email.getText().toString() + " " + idea.getText().toString();
try{
getData(toSubmit);
}catch(IOException e){
e.printStackTrace();
}
}
});
}
public static InputStream toInputStream(String input, String encoding) throws IOException {
byte[] bytes = encoding != null ? input.getBytes(encoding) : input.getBytes();
return new ByteArrayInputStream(bytes);
}
private static final int DEFAULT_BUFFER_SIZE = 1024 * 4;
public static long copyLarge(InputStream input, OutputStream output)
throws IOException {
byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
long count = 0;
int n = 0;
while (-1 != (n = input.read(buffer))) {
output.write(buffer, 0, n);
count += n;
}
return count;
}
public static int copy(InputStream input, OutputStream output) throws IOException {
long count = copyLarge(input, output);
if (count > Integer.MAX_VALUE) {
return -1;
}
return (int) count;
}
String getData(String postData) throws IOException {
StringBuilder respData = new StringBuilder();
URL url = new URL("MY_URL");
URLConnection conn = url.openConnection();
HttpURLConnection httpUrlConnection = (HttpURLConnection) conn;
httpUrlConnection.setUseCaches(false);
httpUrlConnection.setRequestProperty("User-Agent", "YourApp");
httpUrlConnection.setConnectTimeout(30000);
httpUrlConnection.setReadTimeout(30000);
httpUrlConnection.setRequestMethod("POST");
httpUrlConnection.setDoOutput(true);
OutputStream os = httpUrlConnection.getOutputStream();
InputStream postStream = toInputStream(postData, "UTF-8");
try {
copy(postStream, os);
} finally {
postStream.close();
os.flush();
os.close();
}
httpUrlConnection.connect();
int responseCode = httpUrlConnection.getResponseCode();
if (200 == responseCode) {
InputStream is = httpUrlConnection.getInputStream();
InputStreamReader isr = null;
try {
isr = new InputStreamReader(is);
char[] buffer = new char[1024];
int len;
while ((len = isr.read(buffer)) != -1) {
respData.append(buffer, 0, len);
}
} finally {
if (isr != null)
isr.close();
Toast toast = Toast.makeText(getApplicationContext(), "Success", Toast.LENGTH_SHORT);
}
is.close();
}
else {
// use below to get error stream
// inputStream = httpUrlConnection.getErrorStream();
}
return respData.toString();
}
}
最佳答案
参见 http://developer.android.com/reference/android/os/AsyncTask.html对于 android 记录的用法,但它基本上归结为以下实现:
一个继承了 AsyncTask 的私有(private)子类,它实现了以下方法:
onPreExecute
– 在任务执行之前在 UI 线程上调用,用于设置内容(例如显示进度条)doInBackground
– 您要执行的实际操作,在 onPreExecute 之后立即触发onPostExecute
– 在 doInBackground 完成后在 UI 线程上调用。这会将 doInBackground 的结果作为参数,然后可以在 UI 线程上使用。
AsyncTask 用于 UI 线程不允许的操作,例如:
- 打开套接字连接
- HTTP 请求(例如 HTTPClient 和 HTTPURLConnection)
- 正在尝试连接到远程 MySQL 数据库
- 下载文件
您当前的代码位于将在 UI 线程上创建的方法中(这将抛出 NetworkOnMainThreadException
,因此您需要将代码移至运行在 上的线程code>worker
线程。
将代码移至 AsyncTask
从表面上看,只有 getData()
方法需要重新排列。与检索数据有关的所有事情都可以放在任务的 doInBackground
位中,所有 UI 组件的更新(例如您的 toast
)都需要移至 onPostExecute
。
它应该看起来像下面这样(注意一些事情可能需要调整。这是在编译器之外编写的):
private class MyTask extends AsyncTask<Void, Void, Value>
{
boolean success = false;
@Override
protected String doInBackground(String toSubmit)
{
StringBuilder respData = new StringBuilder();
URL url = new URL("MY_URL");
URLConnection conn = url.openConnection();
HttpURLConnection httpUrlConnection = (HttpURLConnection) conn;
httpUrlConnection.setUseCaches(false);
httpUrlConnection.setRequestProperty("User-Agent", "YourApp");
httpUrlConnection.setConnectTimeout(30000);
httpUrlConnection.setReadTimeout(30000);
httpUrlConnection.setRequestMethod("POST");
httpUrlConnection.setDoOutput(true);
OutputStream os = httpUrlConnection.getOutputStream();
InputStream postStream = toInputStream(toSubmit, "UTF-8");
try {
copy(postStream, os);
} finally {
postStream.close();
os.flush();
os.close();
}
httpUrlConnection.connect();
int responseCode = httpUrlConnection.getResponseCode();
if (200 == responseCode) {
InputStream is = httpUrlConnection.getInputStream();
InputStreamReader isr = null;
try {
isr = new InputStreamReader(is);
char[] buffer = new char[1024];
int len;
while ((len = isr.read(buffer)) != -1) {
respData.append(buffer, 0, len);
}
} finally {
if (isr != null)
{
isr.close();
success = true;
}
}
is.close();
}
else {
// use below to get error stream
// inputStream = httpUrlConnection.getErrorStream();
}
return respData.toString();
}
@Override
protected void onPostExecute(String result)
{
Toast toast = Toast.makeText(getApplicationContext(), "Success", Toast.LENGTH_SHORT);
processValue(result);
}
}
private void processValue(String theResult)
{
//handle value
}
String toSubmit = "";
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
ButterKnife.bind(this);
submit.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
//get input from editText boxes to send to php file on server
toSubmit = name.getText().toString() + " " + email.getText().toString() + " " + idea.getText().toString();
try{
new MyTask().execute();
}catch(IOException e){
e.printStackTrace();
}
}
});
}
关于php - android.os.NetworkOnMainThreadException : refactoring code to use AsyncTask?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/33600303/