Android开发中一些直接拿来用的代码片段

1.再按一次退出程序：

private long exitTime = 0;
@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK
&& event.getAction() == KeyEvent.ACTION_DOWN) {
if ((System.currentTimeMillis() - exitTime) > 2000) {
Toast.makeText(getApplicationContext(), "再按一次退出程序",
Toast.LENGTH_SHORT).show();
exitTime = System.currentTimeMillis();
} else {
finish();
System.exit(0);
}
return true;
}
return super.onKeyDown(keyCode, event);
}

2.webview的activity中按返回键返回到上次浏览的页面：

@Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) {
if (webview.canGoBack()) {
webview.goBack();
} else {
this.finish();
}
return true;
} else {
return super.onKeyDown(keyCode, event);
}
}

3.判断终端是否联网：

public static boolean canConnect(Context context){
ConnectivityManager cManager=(ConnectivityManager)context.getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo info = cManager.getActiveNetworkInfo();
if (info != null && info.isAvailable()){
//能联网
return true;
}else{
//不能联网
return false;
}
}

4.通过访问的接口以及传入的键值对得到服务器返回的数据：

public static String getData(String url, List<NameValuePair> nameValuePairs) throws JSONException {
if (nameValuePairs == null) {
nameValuePairs = new ArrayList<NameValuePair>();
}
String data = "";
StringBuffer stringBuffer = new StringBuffer();
try {
HttpEntity httpEntity = new UrlEncodedFormEntity(nameValuePairs,
"utf-8");
System.out.println("访问的接口是： ----》" + url);
HttpPost post = new HttpPost(url);
post.setEntity(httpEntity);
System.out.println("HttpEntity is : "
+ new BufferedReader(new InputStreamReader(httpEntity
.getContent())).readLine());
HttpClient client = getHttpClient();
HttpResponse response = client.execute(post);
if (response.getStatusLine().getStatusCode() == 200) {
BufferedReader reader = new BufferedReader(
new InputStreamReader(response.getEntity().getContent()));
String line;
while ((line = reader.readLine()) != null) {
stringBuffer.append(line);
}
} else
return null;
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (ConnectTimeoutException e) {
return null;
} catch (IOException e) {
e.printStackTrace();
}
data = stringBuffer.toString();
return parseData(data);
}

private static HttpClient getHttpClient() {
HttpClient client = new DefaultHttpClient();
client.getParams().setIntParameter(HttpConnectionParams.SO_TIMEOUT,
20000); // 超时设置
client.getParams().setIntParameter(
HttpConnectionParams.CONNECTION_TIMEOUT, 20000);// 连接超时
return client;
}

4.通过Url得到数据：

/**
* @param url
* @throws IOException
*/
public static String getDataFromUrl(String url) throws IOException {
String result = "";
URL uri = new URL(url);
HttpURLConnection conn = (HttpURLConnection) uri.openConnection();
if(conn.getResponseCode() == 200){
String encode = conn.getContentEncoding();
InputStream in = conn.getInputStream();
result = getStrFromInput(in, encode);
}
return result;
}

5.通过输入流得到String

/**
* @param in
* @param encode
* @return
* @throws IOException
*/
private static String getStrFromInput(InputStream in, String encode) throws IOException {

ByteArrayOutputStream out = new ByteArrayOutputStream();

byte[] buffer = new byte[1024];

int len = 0;

while((len = in.read(buffer)) != -1){
out.write(buffer, 0, len);
}
out.flush();
out.close();
return new String(out.toByteArray(), "UTF-8");
}