Question

我正在为android构建货币转换器并在此代码中获取空指针异常。我正在转换所有值，因为在编辑文本中输入了数字，文本视图中的所有值都被更改。请帮助!! ！

public class MainActivity extends Activity {
EditText currency;
String value;
float us,pk,om,ks,e;
TextView usa,pak,uk,oman,ksa,eu;
float val;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        value=currency.getText().toString();
        usa=(TextView)findViewById(R.id.textView1);
        pak=(TextView)findViewById(R.id.textView2);
        uk=(TextView)findViewById(R.id.textView3);
        oman=(TextView)findViewById(R.id.textView4);
        ksa=(TextView)findViewById(R.id.textView5);
        eu=(TextView)findViewById(R.id.textView6);

        currency=(EditText)findViewById(R.id.editText1);
        currency.addTextChangedListener(new TextWatcher() {

            public void onTextChanged(CharSequence s, int start, int before,
            int count) {

                value=currency.getText().toString();
            //  Toast.makeText(getApplicationContext(),value, Toast.LENGTH_SHORT).show();

                try {
                   val = Float.parseFloat(value);
                   us=val*3.67f;
                   usa.setText(Float.toString(us));
                   pk=val=26.95f*val;
                   pak.setText(Float.toString(pk));
                   om=val*0.10f;
                   oman.setText(Float.toString(om));

                   ks=val*1.02f;
                   ksa.setText(Float.toString(ks));

                   e=val*0.20f;

                   eu.setText(Float.toString(e));
                }


            catch(NumberFormatException ex) {
                        val = 0.0f; 
                        usa.setText("0");
                        pak.setText("0");
                        uk.setText("0");
                        oman.setText("0");
                        ksa.setText("0");
                        eu.setText("0");
                    }
                    Toast.makeText(getApplicationContext(),Float.toString(val), Toast.LENGTH_SHORT).show();


                    //us=val*3.67;
                }

                public void beforeTextChanged(CharSequence s, int start, int count,
                int aft

er) {

            }

            public void afterTextChanged(Editable s) {

            }
            });




        //val=Double.parseDouble(value);
    //  us=val*3.67;
    //  usa.setText(String.valueOf(us));
    }

跟踪：

    08-12 17:35:03.846: E/AndroidRuntime(2944): FATAL EXCEPTION: main
08-12 17:35:03.846: E/AndroidRuntime(2944): java.lang.RuntimeException: Unable to start activity ComponentInfo{omnia.android.nfc/omnia.android.nfc.MainActivity}: java.lang.NullPointerException
08-12 17:35:03.846: E/AndroidRuntime(2944):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at android.app.ActivityThread.access$700(ActivityThread.java:140)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at android.os.Handler.dispatchMessage(Handler.java:99)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at android.os.Looper.loop(Looper.java:137)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at android.app.ActivityThread.main(ActivityThread.java:4921)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at java.lang.reflect.Method.invokeNative(Native Method)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at java.lang.reflect.Method.invoke(Method.java:511)
08-12 17:35:03.846: E/AndroidRuntime(2944):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)

Answer 1

...

currency=(EditText)findViewById(R.id.editText1);

value=currency.getText().toString();
usa=(TextView)findViewById(R.id.textView1);
pak=(TextView)findViewById(R.id.textView2);
uk=(TextView)findViewById(R.id.textView3);
oman=(TextView)findViewById(R.id.textView4);
ksa=(TextView)findViewById(R.id.textView5);
eu=(TextView)findViewById(R.id.textView6);

...

在此处移动货币。

您正试图在不启动货币数据的情况下获取货币数据。

货币转换器Android应用程序中的空指针异常

1 个答案: