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这是我的代码：行号。94 对应于我获取所有 id 的方法。
我总是收到一个错误：您的应用程序已意外停止。

package karan.app.caloriecalculator;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.View;
import android.widget.AdapterView;

import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;

public class Main extends Activity implements AdapterView.OnItemSelectedListener {

Button bcal;
TextView intro, choose, duration, min, weight, kg;
EditText dur, weigh;
Spinner sel;
String temp;
public double w, d, calories;
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    get_all_ids();
    setArrayAdapter();
    sel.setOnItemSelectedListener(this);

    bcal.setOnClickListener(new View.OnClickListener() {

        public void onClick(View v) {

            // TODO Auto-generated method stub
            w = Float.valueOf(weigh.getText().toString());
            d = Float.valueOf(dur.getText().toString());

            if (temp.contentEquals("Aerobics:general")){
                calories = 0.11*w*d;
            }
            else if (temp.contentEquals("Badminton")){
                calories = (w/13)*d;
            }
            else if (temp.contentEquals("Basketball")){
                calories = (w/7.45)*d;
            }
            else if (temp.contentEquals("Bicycling:slow (10-12 mph)")){
                calories = (w/9.65)*d;
            }
            else if (temp.contentEquals("Bicycling:general (12-14 mph)")){
                calories = (w/7.2)*d;
            }
            else if (temp.contentEquals("Bicycling:moderate (14-16 mph)")){
                calories = (w/6)*d;
            }
            else if (temp.contentEquals("Bicycling:fast (16+ mph)")){
                calories = (w/5)*d;
            }
            else if (temp.contentEquals("Bowling")){
                calories = (w/19.1)*d;
            }
            else if (temp.contentEquals("Boxing: punching bag")){
                calories = (w/9.6)*d;
            }
            else if (temp.contentEquals("Boxing: sparring")){
                calories = (w/6.375)*d;
            }



    /*  Thread t = new Thread(){
        public void run(){
        try{
            sleep(1);
        }
        catch (InterruptedException e){
            e.printStackTrace();
        }
        finally{
        Intent openResult = new Intent("karan.app.caloriecalculator.RESULT");
        startActivity(openResult);
        }
        }
        };   // close the thread with a ;

        */
        }});


}


public void get_all_ids() {
    bcal.findViewById(R.id.b1);
    intro.findViewById(R.id.tv1);
    choose.findViewById(R.id.tv2);
    duration.findViewById(R.id.tv3);
    min.findViewById(R.id.tv4);
    weight.findViewById(R.id.tv5);
    kg.findViewById(R.id.tv6);
    dur.findViewById(R.id.et2);
    weigh.findViewById(R.id.et1);
    sel.findViewById(R.id.sp1);

}



public double getCalories() {
    return calories;
}



public void setArrayAdapter(){

    //The createFromResource() method allows you to create an ArrayAdapter from the string array
    ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.choices, android.R.layout.simple_spinner_dropdown_item);
    //You should then call setDropDownViewResource(int) to specify the layout the adapter should use to display the list of spinner choices
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    //Call setAdapter() to apply the adapter to your Spinner.
    sel.setAdapter(adapter);       
}



public void onItemSelected(AdapterView<?> parent, View view, int position,
        long id) {
    // TODO Auto-generated method stub
      Object item = parent.getItemAtPosition(position);
      temp = item.toString();

}



public void onNothingSelected(AdapterView<?> arg0) {
    // TODO Auto-generated method stub

}

}

日志猫：

07-28 14:10:03.545: E/AndroidRuntime(266):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
07-28 14:10:03.545: E/AndroidRuntime(266):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
07-28 14:10:03.545: E/AndroidRuntime(266):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
07-28 14:10:03.545: E/AndroidRuntime(266):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
07-28 14:10:03.545: E/AndroidRuntime(266):  at android.os.Handler.dispatchMessage(Handler.java:99)
07-28 14:10:03.545: E/AndroidRuntime(266):  at android.os.Looper.loop(Looper.java:123)
07-28 14:10:03.545: E/AndroidRuntime(266):  at android.app.ActivityThread.main(ActivityThread.java:4627)
07-28 14:10:03.545: E/AndroidRuntime(266):  at java.lang.reflect.Method.invokeNative(Native Method)
07-28 14:10:03.545: E/AndroidRuntime(266):  at java.lang.reflect.Method.invoke(Method.java:521)
07-28 14:10:03.545: E/AndroidRuntime(266):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
07-28 14:10:03.545: E/AndroidRuntime(266):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
07-28 14:10:03.545: E/AndroidRuntime(266):  at dalvik.system.NativeStart.main(Native Method)
07-28 14:10:03.545: E/AndroidRuntime(266): Caused by: java.lang.NullPointerException
07-28 14:10:03.545: E/AndroidRuntime(266):  at karan.app.caloriecalc.MainActivity.get_all_ids(MainActivity.java:96)
07-28 14:10:03.545: E/AndroidRuntime(266):  at karan.app.caloriecalc.MainActivity.onCreate(MainActivity.java:28)
07-28 14:10:03.545: E/AndroidRuntime(266):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
07-28 14:10:03.545: E/AndroidRuntime(266):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
07-28 14:10:03.545: E/AndroidRuntime(266):  ... 11 more
4

1 回答 1

1

您在 get_all_ids() 中错误地获取视图。

要获得视图，您必须执行以下操作：

TextView intro;
public void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      intro = (TextView) findViewById(R.id.tv1);
      ....
}
// You can now use intro and methods of TextView class.

我建议您阅读Android 初学者指南。

于 2012-07-28T09:42:16.140 回答