如何将getResources（）用于非活动类

Question

I am trying to validate my text box. I have created a Java class which has the validation. I am using setError(MSG, icon);

Something like this:

public class Validate
{

public static boolean hasText(EditText editText) 
{
    String text = editText.getText().toString().trim();
    editText.setError(null);

    if (text.length() == 0) 
    {
        errorIcon = context.getResources().getDrawable(R.drawable.alert);
        errorIcon.setBounds(new Rect(0, 0, errorIcon.getIntrinsicWidth(), errorIcon.getIntrinsicHeight()));
        editText.setError((REQUIRED_MSG), errorIcon);
        return false;
    }

    return true;
   }
 }

And my activity java file has this:

    @Override
protected void onCreate(Bundle savedInstanceState) 
{       
        fname =(EditText)findViewById(R.id.fname);
        fname.addTextChangedListener(new TextWatcher() {
        public void afterTextChanged(Editable s) 
        {
            Validate.hasText(fname);
        }
        public void beforeTextChanged(CharSequence s, int start, int count, int after){}
        public void onTextChanged(CharSequence s, int start, int before, int count){}
    });

I tried the following:

public Validate(Context context) 
{
  this.context = context;
 }
}

I get the following error:

02-23 13:30:58.718: E/AndroidRuntime(1334): FATAL EXCEPTION: main
02-23 13:30:58.718: E/AndroidRuntime(1334): java.lang.NullPointerException
02-23 13:30:58.718: E/AndroidRuntime(1334):     at com.zin.testText.Text_Validate.hasText(Text_Validate.java:65)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at com.zin.testText.Text_Form$1.afterTextChanged(Text_Form.java:107)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.widget.TextView.sendAfterTextChanged(TextView.java:7320)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.widget.TextView$ChangeWatcher.afterTextChanged(TextView.java:9073)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.text.SpannableStringBuilder.sendAfterTextChanged(SpannableStringBuilder.java:970)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:497)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:435)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.text.SpannableStringBuilder.replace(SpannableStringBuilder.java:30)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.view.inputmethod.BaseInputConnection.replaceText(BaseInputConnection.java:673)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.view.inputmethod.BaseInputConnection.commitText(BaseInputConnection.java:197)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at com.android.internal.widget.EditableInputConnection.commitText(EditableInputConnection.java:183)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at com.android.internal.view.IInputConnectionWrapper.executeMessage(IInputConnectionWrapper.java:279)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at com.android.internal.view.IInputConnectionWrapper$MyHandler.handleMessage(IInputConnectionWrapper.java:77)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.os.Looper.loop(Looper.java:137)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at android.app.ActivityThread.main(ActivityThread.java:5103)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at java.lang.reflect.Method.invokeNative(Native Method)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at java.lang.reflect.Method.invoke(Method.java:525)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
02-23 13:30:58.718: E/AndroidRuntime(1334):     at dalvik.system.NativeStart.main(Native Method)

Can somebody help me to fix this?

Answer 1

No need to pass Context separately to access getResources() method. Because already passing EditText view to hasText so use editText.getContext() to call getResources() method:

errorIcon = editText.getContext().getResources().getDrawable(R.drawable.alert);

Answer 2

you can take a extra variable context in your method like below code and call that method from your activity pass activity context on this method.

public static boolean hasText(EditText editText ,Context context) 
{
    String text = editText.getText().toString().trim();
    editText.setError(null);

    if (text.length() == 0) 
    {
        errorIcon = context.getResources().getDrawable(R.drawable.alert);
        errorIcon.setBounds(new Rect(0, 0, errorIcon.getIntrinsicWidth(), errorIcon.getIntrinsicHeight()));
        editText.setError((REQUIRED_MSG), errorIcon);
        return false;
    }

    return true;
   } 

Answer 3

You can override Application class, set a static variable to the application instance gInstance in Application.onCreate() and then call gInstance.getResources() .

Yes, the static variable thing is ugly, but you application object will always be available as long as your app is running. As soon as the app is not running, you won't need resources any more.