我试图运行一个活动，以便将所有文本信息提交到mysql数据库并开始一个新的活动，但我总是很遗憾，应用程序已停止
下面是DonateFood.java活动
public class DonateFood extends AppCompatActivity {
EditText txt_title, txt_desc, txt_amount, txt_date;
Spinner statuss;
Button btnSubmit;
String array;
String title, amount, desc, date, status;
Context con;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_donate_food);
txt_title = (EditText)findViewById(R.id.txt_title);
txt_amount = (EditText)findViewById(R.id.txt_amount);
txt_desc = (EditText)findViewById(R.id.txt_desc);
txt_date = (EditText)findViewById(R.id.txt_date);
statuss = (Spinner)findViewById(R.id.status);
btnSubmit = (Button) findViewById(R.id.btnSubmit);
statuss.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
@Override
public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
array=adapterView.getSelectedItem().toString();
}
@Override
public void onNothingSelected(AdapterView<?> adapterView) {
}
});
btnSubmit.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
title = txt_title.getText().toString();
amount = txt_amount.getText().toString();
desc = txt_desc.getText().toString();
date = txt_date.getText().toString();
String method = "addFood";
AddFood addFood = new AddFood(con);
addFood.execute(method,title,amount,desc,date,array);
}
});
}
public class AddFood extends AsyncTask<String, Void, String> {
Context ctx;
final String TAG = this.getClass().getName();
//constructor
AddFood(Context ctx){
this.ctx=ctx;
}
@Override
protected String doInBackground(String... params) {
String food_url = "http://10.0.3.2/MySqlDemo/addFood.php";
String method = params[0];
if(method.equals("addFood")){
String title = params[1];
String amount = params[2];
String desc = params[3];
String date = params[4];
String array = params[5];
try {
URL url = new URL (food_url);
HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setDoOutput(true);
httpURLConnection.setDoInput(true);
OutputStream outputStream = httpURLConnection.getOutputStream();
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
String data = URLEncoder.encode("title", "UTF-8")+"="+URLEncoder.encode(title, "UTF-8")+ "&"
+URLEncoder.encode("amount", "UTF-8")+"="+URLEncoder.encode(amount, "UTF-8")+ "&"
+URLEncoder.encode("desc", "UTF-8")+"="+URLEncoder.encode(desc, "UTF-8")+ "&"
+URLEncoder.encode("date", "UTF-8")+"="+URLEncoder.encode(date, "UTF-8")+ "&"
+URLEncoder.encode("array", "UTF-8")+"="+URLEncoder.encode(array, "UTF-8");
bufferedWriter.flush();
bufferedWriter.close();
outputStream.close();
InputStream inputStream = httpURLConnection.getInputStream();
inputStream.close();
return "Food added successfully";
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
@Override
protected void onPreExecute() {
super.onPreExecute();
}
@Override
protected void onPostExecute(String result) {
if (result == null) {
Toast.makeText(ctx,"result was null", Toast.LENGTH_SHORT).show();
return;
}
else if (result.equals("Food added successfully")) {
Toast.makeText(ctx, result, Toast.LENGTH_SHORT).show();
ctx.startActivity(new Intent(ctx, FoodView.class));
}
}
}
}
logcat错误：
02-24 17:21:45.465 5871-5871/alsaad.layla.mysqldemo E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException
at android.widget.Toast.<init>(Toast.java:92)
at android.widget.Toast.makeText(Toast.java:238)
at alsaad.layla.mysqldemo.DonateFood$AddFood.onPostExecute(DonateFood.java:161)
at alsaad.layla.mysqldemo.DonateFood$AddFood.onPostExecute(DonateFood.java:90)
at android.os.AsyncTask.finish(AsyncTask.java:631)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
最佳答案
尝试在您的getApplicationContext()中使用onPostExecute（）
Toast.makeText(getApplicationContext(),"result was null", Toast.LENGTH_SHORT).show();
而不是：
Toast.makeText(ctx,"result was null", Toast.LENGTH_SHORT).show();
关于java - 未在mysql数据库中添加postExecute方法URL参数的Android错误，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/42445179/