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我在ViewPager的工具欄onCreateOptionsMenu中從數據庫填充了一個微調器，我想將它的值傳遞給fragment。如何將工具欄微調器中的值傳遞給ViewPager片段
我想要實現的是根據微調器值更改片段內容。 我試圖通過捆綁傳遞這個值，但它會拋出我null object reference ...
我敢打賭，因爲片段和它的東西比我的微調器加載速度快，它的價值在捆綁。即使如此，我不知道如何以正確的方式通過這個值...
在此先感謝您的幫助！
編輯：
我找到了解決問題的方法，但我打了另一個。我不能發送纈更多的null以外的活動。
ChartsActivity.java
public class ChartsAcivity extends AppCompatActivity {
Context context = this;
int selected_car_id = 0;
DBHelper dbHelper;
String spinnerValue = null;
private ViewPager mViewPager;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.charts_acivity);
Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
setSupportActionBar(toolbar);
if (getSupportActionBar() != null){
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
getSupportActionBar().setDisplayShowHomeEnabled(true);
}
SectionsPagerAdapter mSectionsPagerAdapter = new SectionsPagerAdapter(getSupportFragmentManager());
Chart1Activity chart1 = (Chart1Activity) mSectionsPagerAdapter.getItem(0);
if (spinnerValue != null) chart1.respond("test");
else chart1.respond("OMG EMPTY AGAIN?!?!");
mViewPager = (ViewPager) findViewById(R.id.container);
mViewPager.setAdapter(mSectionsPagerAdapter);
TabLayout tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(mViewPager);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.menu_charts_acivity, menu);
MenuItem carSpinner = menu.findItem(R.id.charts_activ_car_spinner);
Spinner CarRefuelListSpinner = (Spinner) MenuItemCompat.getActionView(carSpinner);
SQLiteDatabase db = new DBHelper(this).getWritableDatabase();
Cursor spinner_cursor = db.rawQuery("SELECT " + TableCar.NewCar.CAR_ID + " AS _id, " + TableCar.NewCar.CAR_NAME + " FROM " + TableCar.NewCar.TABLE_NAME, null);
if(spinner_cursor.moveToFirst()) {
String[] from = new String[]{TableCar.NewCar.CAR_NAME};
int[] to = new int[]{android.R.id.text1};
SimpleCursorAdapter simpleCursorAdapter = new SimpleCursorAdapter(this, android.R.layout.simple_spinner_item, spinner_cursor, from, to);
simpleCursorAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
CarRefuelListSpinner.setAdapter(simpleCursorAdapter);
CarRefuelListSpinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
public void onItemSelected(AdapterView<?> parent, View view, int position, long id) {
((TextView) parent.getChildAt(0)).setTextColor(Color.WHITE);
selected_car_id = Integer.valueOf(String.valueOf(id));
String s = String.valueOf(selected_car_id);
getSpinnerVal(s);
//chart1.respond("test");
//Chart1Activity chart1 = (Chart1Activity) mSectionsPagerAdapter.getItem(0);
//chart1.respond(s);
}
public void onNothingSelected(AdapterView<?> parent) {
}
});
}
else {
...
}
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
switch (item.getItemId()) {
case android.R.id.home:
onBackPressed();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
public void getSpinnerVal (String value){
spinnerValue = value;
}
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
switch (position){
case 0:
Chart1Activity chart1 = new Chart1Activity();
return chart1;
case 1:
Chart2Activity chart2 = new Chart2Activity();
return chart2;
case 2:
Chart3Activity chart3 = new Chart3Activity();
return chart3;
default:
return null;
}
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "TEST 1";
case 1:
return "TEST 2";
case 2:
return "TEST 3";
}
return null;
}
}
}
Chart1Activity.java
public class Chart1Activity extends Fragment implements FragmentCommunicator{
Context context;// = getActivity();
DBHelper dbHelper;
LineChart chart;
String car_id = null;
String test = null;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.chart1_fragment, container, false);
if (car_id != null) {
chart = (LineChart) getActivity().findViewById(R.id.chart1_line_fuel_usage);
Toast.makeText(getActivity(), "ID = " + car_id, Toast.LENGTH_LONG).show();
setData(car_id);
}
else Toast.makeText(getActivity(), "ID = null", Toast.LENGTH_LONG).show();
return rootView;
}
@Override
public void respond(String data) {
car_id = data;
}
public void setData(String car_id){
dbHelper = new DBHelper(context);
Cursor curChartFuelUsage = dbHelper.getChartFuelUsage(car_id);
curChartFuelUsage.moveToFirst();
int count = curChartFuelUsage.getCount();
final String[] x_refuel_data = new String[count];
final String[] x2_refuel_data = new String[count];
Float[] y_fuel_usage = new Float[count];
if (curChartFuelUsage.moveToFirst()){
for (int i = 0 ; i < count ; i++){
x_refuel_data[i] = curChartFuelUsage.getString(0);
x2_refuel_data[i] = x_refuel_data[i].replace("-", "/");
y_fuel_usage[i] = curChartFuelUsage.getFloat(1);
curChartFuelUsage.moveToNext();
}
ArrayList<Entry> values = new ArrayList<Entry>();
for (int i = 0 ; i < count ; i++){
values.add(new Entry(i, y_fuel_usage[i]));
}
LineDataSet set1 = new LineDataSet(values,"test");
set1.setAxisDependency(YAxis.AxisDependency.LEFT);
set1.setColors(new int[]{R.color.chartRed}, context);
ArrayList<ILineDataSet> dataSets = new ArrayList<ILineDataSet>();
dataSets.add(set1);
LineData lineData = new LineData(dataSets);
chart.setData(lineData);
IAxisValueFormatter formatter = new IAxisValueFormatter() {
@Override
public String getFormattedValue(float value, AxisBase axis) {
return x2_refuel_data[(int)value];
}
@Override
public int getDecimalDigits() {
return 0;
}
};
chart.getXAxis().setValueFormatter(formatter);
chart.invalidate();
}
else Toast.makeText(context, "xxx.", Toast.LENGTH_LONG).show();
}
}
FragmentCommunicator.java
public interface FragmentCommunicator {
public void respond (String data);
}
可能重複[Avoiding！= null statements]（http://stackoverflow.com/questions/271526/avoiding-null-statements） – Chisko