Get Context Java Android example
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getContext() getApplicationContext() method Java Android example source
Context myContext_1 = ThisClassName.this; // to open a Dialog
Context myContext_2 = getContext();
Context myContext_3 = this.getContext();
Context myContext_4 = this;
Context myContext_5 = this.getApplicationContext ();
OnClickListener getImageBtnOnClick = new OnClickListener() {
public void onClick(View view) {
Context context = view.getContext();
}
};
// Toast
Toast.makeText(getApplicationContext(), "Context == getApplicationContext "
, Toast.LENGTH_SHORT).show();
// store Context in public class
public class MyActivity extends Activity {
public static Context myCnt = null;
...
protected void onCreate(Bundle icicle) {
...
myCnt = this;
MyStorage.setContext(myCnt);
// or
// MyStorage.setContext(this);
// cntxFromStorage == this
Context cntxFromStorage = MyStorage.getContext();
...
};
};
public class MyStorage
{
private static Context cntStorageContext = null;
public static Context getContext() {
return cntStorageContext;
}
public static void setContext(Context context) {
MyStorage.cntStorageContext = context;
}
};
class DataBaseHelper extends SQLiteOpenHelper {
// get MyActivity context
Context cnt = MyStorage.getContext();
}
397LW NO topic_id
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Další témata ....(Topics)
Physical pixel (px)
Density independent pixel (dp)
Dots per inch (dpi) .. physical pixels per inch
px = dp * (dpi / 160)
Density independent pixel (dp)
Dots per inch (dpi) .. physical pixels per inch
px = dp * (dpi / 160)
public static int dpToPx(int dp)
{
return (int) (dp * Resources.getSystem().getDisplayMetrics().density);
}
public static int pxToDp(int px)
{
return (int) (px / Resources.getSystem().getDisplayMetrics().density);
}
public class MainActivity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(new SampleView(this));
}
private static class SampleView extends View {
// CONSTRUCTOR
public SampleView(Context context) {
super(context);
setFocusable(true);
}
@Override
protected void onDraw(Canvas canvas) {
//drawARGB (int a, int r, int g, int b)
// a alpha component (0..255) of the color to draw onto the canvas
// r red component (0..255)
// g green component (0..255)
// b blue component (0..255)
canvas.drawARGB(255, 0, 255, 10);
}
}
}
If You create new xml file with prefix _ , for example _style.xml and You to clean project (Project->Clean), than package in folder project\gen will deleted with R.java class and new R.java not be created.
For to solving this problem You have to rename file without prefix _ as style.xml or name what You need and rebuild project.
If some ID cannot be resolved or is not a field get error occurence
You have to delete import android.R; in Activity.class if was inserted,
when this error is displayed.
For to solving this problem You have to rename file without prefix _ as style.xml or name what You need and rebuild project.
If some ID cannot be resolved or is not a field get error occurence
You have to delete import android.R; in Activity.class if was inserted,
when this error is displayed.
onSaveInstanceState, onRestoreInstanceState , save preferences
int mCurrentPhotoIndex = 0;
@Override
protected void onSaveInstanceState(Bundle outState) {
outState.putInt("photo_index", mCurrentPhotoIndex);
super.onSaveInstanceState(outState);
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
mCurrentPhotoIndex = savedInstanceState.getInt("photo_index");
super.onRestoreInstanceState(savedInstanceState);
}
// or save preferences for new start of Activity in onStop
//onCreate or onResume or onStart etc.
public void loadPreferences() {
SharedPreferences settings = getSharedPreferences(F.PREFERENCES_NAME, 0);
mCurrentPhotoIndex = settings.getInt("mCurrentPhotoIndex",mCurrentPhotoIndex);
// String_sOtazka = settings.getString("_sOtazka", _sOtazka);
}
// onStop
public void savePreferences() {
SharedPreferences settings = getSharedPreferences(PREFERENCES_NAME, 0);
SharedPreferences.Editor editor = settings.edit();
editor.putInt("mCurrentPhotoIndex", mCurrentPhotoIndex);
// String, boolean, float ...
// editor.putString("mButton1", mButton1.getText().toString());
editor.commit();
}
xml example source code with image.
<TableLayout android:layout_width="match_parent" android:id="@+id/idTableInRadioGroup" android:layout_height="wrap_content">
<TableRow android:id="@+id/tableRow1" android:layout_width="wrap_content" android:layout_height="wrap_content">
<RadioGroup android:id="@+id/idRadio_group_1_column"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:orientation="vertical">
<RadioButton android:id="@+id/idRadio_1"
android:text="@string/textLabel_1"/>
<RadioButton android:id="@+id/idRadio_2"
android:text="@string/textLabel_2"/>
<RadioButton android:id="@+id/idRadio_3"
android:text="@string/textLabel_3"/>
</RadioGroup>
<RadioGroup android:id="@+id/idRadio_group_2_column"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginLeft="20dp"
android:orientation="vertical">
<RadioButton android:id="@+id/idRadio_4"
android:text="@string/textLabel_4"/>
<RadioButton android:id="@+id/idRadio_5"
android:text="@string/textLabel_5"/>
<RadioButton android:id="@+id/idRadio_6"
android:text="@string/textLabel_6"/>
</RadioGroup>
</TableRow>
</TableLayout>
Editace: 2011-10-15 08:31:19
Počet článků v kategorii: 397
Url:get-context-java-android-example
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