我正在制作一个简单的android应用程序来存储纬度和经度mysql数据库。我已经创建了一个本地数据库。数据库有3个字段id，它是自动递增的，还有两个字段lat2（float）和lng2（float。
这是我的日志错误
12-28 16:45:04.470: D/gralloc_goldfish(1400): Emulator without GPU emulation detected.
12-28 16:45:11.190: D/AndroidRuntime(1400): Shutting down VM
12-28 16:45:11.190: W/dalvikvm(1400): threadid=1: thread exiting with uncaught exception (group=0xb3a71ba8)
12-28 16:45:11.320: E/AndroidRuntime(1400): FATAL EXCEPTION: main
12-28 16:45:11.320: E/AndroidRuntime(1400): Process: com.example.test, PID: 1400
12-28 16:45:11.320: E/AndroidRuntime(1400): java.lang.NullPointerException
12-28 16:45:11.320: E/AndroidRuntime(1400): at com.example.test.MainActivity$1.onClick(MainActivity.java:51)
12-28 16:45:11.320: E/AndroidRuntime(1400): at android.view.View.performClick(View.java:4438)
12-28 16:45:11.320: E/AndroidRuntime(1400): at android.view.View$PerformClick.run(View.java:18422)
12-28 16:45:11.320: E/AndroidRuntime(1400): at android.os.Handler.handleCallback(Handler.java:733)
12-28 16:45:11.320: E/AndroidRuntime(1400): at android.os.Handler.dispatchMessage(Handler.java:95)
12-28 16:45:11.320: E/AndroidRuntime(1400): at android.os.Looper.loop(Looper.java:136)
12-28 16:45:11.320: E/AndroidRuntime(1400): at android.app.ActivityThread.main(ActivityThread.java:5001)
12-28 16:45:11.320: E/AndroidRuntime(1400): at java.lang.reflect.Method.invokeNative(Native Method)
12-28 16:45:11.320: E/AndroidRuntime(1400): at java.lang.reflect.Method.invoke(Method.java:515)
12-28 16:45:11.320: E/AndroidRuntime(1400): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
12-28 16:45:11.320: E/AndroidRuntime(1400): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
12-28 16:45:11.320: E/AndroidRuntime(1400): at dalvik.system.NativeStart.main(Native Method)
12-28 16:45:17.380: I/Process(1400): Sending signal. PID: 1400 SIG: 9
这是我的主要活动
package com.example.test;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONObject;
import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends Activity {
private float lat;
private float lng;
private String lat2;
private String lng2;
MainActivity gps;
private String line;
Button btninsert;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btninsert = (Button) findViewById(R.id.button1);
btninsert.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(gps.canGetLocation()){
lat = (float) gps.getLatitude();
lng = (float) gps.getLongitude();
lat2= String.valueOf(lat);
lng2= String.valueOf(lng);
Toast.makeText(getApplicationContext(), "Success insert - 'nLat: " + lat2 + "'nLong: " + lng2, Toast.LENGTH_LONG).show();
}else{
// can't get location
// GPS or Network is not enabled
// Ask user to enable GPS/network in settings
gps.showSettingsAlert();
}
}});
}
protected void showSettingsAlert() {
// TODO Auto-generated method stub
}
protected float getLatitude() {
// TODO Auto-generated method stub
return 0;
}
protected float getLongitude() {
// TODO Auto-generated method stub
return 0;
}
protected boolean canGetLocation() {
// TODO Auto-generated method stub
return false;
}
public void insert(String result, String lat2,String lng2) {
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("lat2", lat2));
nameValuePairs.add(new BasicNameValuePair("lng2", lng2));
InputStream is = null;
try {
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost("http://192.168.1.31/insert_android.php");
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
Log.e("pass 1", "connection success ");
} catch (Exception e) {
Log.e("Fail 1", e.toString());
Toast.makeText(getApplicationContext(), "Invalid IP Address",
Toast.LENGTH_LONG).show();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
while ((line = reader.readLine()) != null) {
sb.append(line + "'n");
}
is.close();
result = sb.toString();
Log.e("pass 2", "connection success ");
} catch (Exception e) {
Log.e("Fail 2", e.toString());
}
try {
JSONObject json_data = new JSONObject(result);
lng2 = (json_data.getString("code"));
if (lng2 == null) {
Toast.makeText(getBaseContext(), "Inserted Successfully",
Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(getBaseContext(), "Sorry, Try Again",
Toast.LENGTH_LONG).show();
}
} catch (Exception e) {
Log.e("Fail 3", e.toString());
}
}
}
这是我的php脚本
<?php
$hostname = 'localhost';
$username = 'root';
$password = '';
$conn = mysql_connect($hostname,$username,$password) or die('Blah');
if ($conn) {
mysql_select_db("test", $conn);
// extract your data
if (isset($_POST['lat']) && isset($_POST['lng']) ){
$lat2 = $_POST['lat'];
$lng2 = $_POST['lng'];
$query2 = "INSERT INTO markers_awal VALUES('','$lat2','$lng2')";
if (mysql_query($query2, $conn))
echo "data inserted";
else {
echo "Oh dear " . mysql_error();
}
}
}
?>
老兄，你有一个名为gps的对象，它属于MainActivity，实际上与你所在的活动相同。
所以有两个问题，
- 您根本不需要那个
gps对象。只需在没有CCD_ 5的情况下调用CCD_ - 其次，如果你真的想保留那个奇怪的
gps对象，那么你必须为它分配一个值，在你的情况下就是gps = this;
那肯定能解决你的NullPointerException
我希望这能有所帮助。
您正在使用gps类，那么您在哪里初始化gps？如果你不初始化gps，那么初始化它。我还观察到，在setContentView方法之前，你的代码中没有超级构造函数。把这个放到你的代码里。
super.onCreate(savedInstanceState);
使用方法将浮点值转换为String
String lat2 = String.valueOf(lat);
String lng2 = String.valueOf(lng);
请确保这些值有一定的价值。使用日志或toast消息进行检查。
在第51行出现错误。这实际上是你的onclick方法。您是否可以检查canGetLocation（）方法每次返回的值是否为false。根据您的logcat，您还会得到一个空指针异常。将onclick方法中的所有数据放入try-catch块中。