【发布时间】：2018-05-20 05:57:21
【问题描述】：
问题是我有一个仪表板，它将显示 6 条生产线的数据，并且可以在 textviews 中查看进度。
但是，文本视图的数据来自一系列 IF 语句和在另一个活动上执行的计算。
当我运行应用程序时，因为仪表板试图在第二个activity 设置数据之前读取数据，有空指针是可以理解的，因为我什至没有机会进入第二个@ 987654323@还没有。
为了妥协，我不得不将仪表板上的 IF 语句设置为按钮，但是，这妨碍了我的应用程序的可用性，我希望数据在仪表板上自动刷新，而无需按下按钮。
在第二个活动中，我将值保存到共享首选项，然后在仪表板上，我获取共享首选项并将其设置为文本视图，但由于仪表板是第一个屏幕，因此仍然为空。
行详细信息 Java：（返回仪表板的主页按钮）：
SharedPreferences.Editor editor = getActivity().getSharedPreferences(MyPREFERENCES, MODE_PRIVATE).edit();
if (spinnerSelection == null || spinnerSelection2 == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Data Input Error");
builder.setMessage("Line S2 Data has not been entered yet!");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (spinnerSelection.equals("S1") && spinnerSelection2.equals("20")) {
if (actualshippersnum > optimum20) {
plus20 = (int) (actualshippersnum - optimum20);
editor.putInt("Key1", plus20);
Toast.makeText(getActivity(), "Line S1 ahead by: " + (plus20) + " shippers", Toast.LENGTH_LONG).show();
} else if (actualshippersnum < optimum20) {
minus20 = (int) (optimum20 - actualshippersnum);
editor.putInt("Key2", minus20);
Toast.makeText(getActivity(), "Line S1 behind by: " + (minus20) + " shippers", Toast.LENGTH_LONG).show();
} else if (actualshippersnum == optimum20) {
editor.putInt("Key3", percentageActual20);
Toast.makeText(getActivity(), "Line S1 is on target at!", Toast.LENGTH_LONG).show();
}
} else if (spinnerSelection.equals("S1") && spinnerSelection2.equals("30")) {
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Refresh Error");
builder.setMessage("Cannot Refresh! Please Fill in Line Details");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (actualshippersnum > optimum30) {
plus30 = (int) (actualshippersnum - optimum30);
editor.putInt("Key 4", plus30);
Toast.makeText(getActivity(), "Line S1 ahead by: " + (plus30) + " shippers", Toast.LENGTH_LONG).show();
} else if (actualshippersnum < optimum30) {
minus30 = (int) (optimum30 - actualshippersnum);
editor.putInt("Key 5", minus30);
Toast.makeText(getActivity(), "Line S1 behind by: " + (minus30) + " shippers", Toast.LENGTH_LONG).show();
} else if (actualshippersnum == optimum30) {
editor.putInt("Key 6", percentageActual30);
Toast.makeText(getActivity(), "Line S1 is on target!", +Toast.LENGTH_LONG).show();
}
}
if (spinnerSelection == null || spinnerSelection2 == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Data Input Error");
builder.setMessage("Line S2 Data has not been entered yet!");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (spinnerSelection.equals("S2") && spinnerSelection2.equals("20")) {
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Refresh Error");
builder.setMessage("Cannot Refresh! Please Fill in Line Details");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (actualshippersnum > optimum20) {
plus20 = (int) (actualshippersnum - optimum20);
editor.putInt("Key 7", plus20);
Toast.makeText(getActivity(), "Line S2 ahead by: " + (plus20) + " shippers", Toast.LENGTH_LONG).show();
} else if (actualshippersnum < optimum20) {
minus20 = (int) (optimum20 - actualshippersnum);
editor.putInt("Key 8", minus20);
Toast.makeText(getActivity(), "Line S2 behind by: " + (minus20) + " shippers", Toast.LENGTH_LONG).show();
} else if (actualshippersnum == optimum20) {
editor.putInt("Key 9", percentageActual20);
Toast.makeText(getActivity(), "Line S2 is on target at!", Toast.LENGTH_LONG).show();
}
} else if (spinnerSelection.equals("S2") && spinnerSelection2.equals("30")) {
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Refresh Error");
builder.setMessage("Cannot Refresh! Please Fill in Line Details");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (actualshippersnum > optimum30) {
plus30 = (int) (actualshippersnum - optimum30);
editor.putInt("Key 10", plus30);
Toast.makeText(getActivity(), "Line S2 ahead by: " + (plus30) + " shippers", Toast.LENGTH_LONG).show();
} else if (actualshippersnum < optimum30) {
minus30 = (int) (optimum30 - actualshippersnum);
editor.putInt("Key 11", minus30);
Toast.makeText(getActivity(), "Line S2 behind by: " + (minus30) + " shippers", Toast.LENGTH_LONG).show();
} else if (actualshippersnum == optimum30) {
editor.putInt("Key 12", percentageActual30);
Toast.makeText(getActivity(), "Line S2 is on target!", +Toast.LENGTH_LONG).show();
}
}
if (spinnerSelection == null || spinnerSelection2 == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Data Input Error");
builder.setMessage("Line S3 Data has not been entered yet!");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (spinnerSelection.equals("S3")) {
if (spinnerSelection2.equals("20")) {
//HAVENT FILLED INTO DECOVIEW - 20
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Refresh Error");
builder.setMessage("Cannot Refresh! Please Fill in Line Details");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else
if (actualshippersnum > optimum20) {
plus20 = (int) (actualshippersnum - optimum20);
editor.putInt("Key 13", plus20);
Toast.makeText(getActivity(), "Line S3 ahead by: " + (plus20)+ " shippers" , Toast.LENGTH_LONG).show();
} else if (actualshippersnum < optimum20) {
minus20 = (int) (optimum20 - actualshippersnum);
editor.putInt("Key 14", minus20);
Toast.makeText(getActivity(), "Line S3 behind by: " + (minus20)+ " shippers" , Toast.LENGTH_LONG).show();
} else if (actualshippersnum == optimum20) {
editor.putInt("Key 15", percentageActual20);
Toast.makeText(getActivity(), "Line S3 is on target!" , Toast.LENGTH_LONG).show();
}
}
else if (spinnerSelection2.equals("30")) {
//HAVENT FILLED INTO DECOVIEW - 30
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
builder.setTitle("Refresh Error");
builder.setMessage("Cannot Refresh! Please Fill in Line Details");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else
if (actualshippersnum > optimum30) {
plus30 = (int) (actualshippersnum - optimum30);
editor.putInt("Key 16", plus30);
Toast.makeText(getActivity(), "Line S3 ahead by: " + (plus30)+ " shippers" ,Toast.LENGTH_LONG).show();
} else if (actualshippersnum < optimum30) {
minus30 = (int) (optimum30 - actualshippersnum);
editor.putInt("Key 17", minus30);
Toast.makeText(getActivity(), "Line S3 behind by: " + (minus30)+ " shippers" , Toast.LENGTH_LONG).show();
} else if (actualshippersnum == optimum30) {
editor.putInt("Key 18", percentageActual30);
Toast.makeText(getActivity(), "Line S3 is on target!", Toast.LENGTH_LONG).show();
}
}
}
}
});
}
仪表板 Java：（恢复时）
public void onResume() {
super.onResume();
int getKey1, getKey2, getKey3, getKey4, getKey5, getKey6, getKey7, getKey8, getKey9, getKey10, getKey11, getKey12, getKey13, getKey14, getKey15, getKey16,getKey17, getKey18;
if (spinnerSelection == null || spinnerSelection2 == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(Dashboard.this);
builder.setTitle("Data Input Error");
builder.setMessage("No SP found!");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (spinnerSelection.equals("S1") && spinnerSelection2.equals("20")) {
if (actualshippersnum > optimum20) {
getKey1 = sharedPreferences.getInt("Key1", plus20);
bar4.setText(getKey1);
} else if (actualshippersnum < optimum20) {
getKey2 = sharedPreferences.getInt("Key2", minus20);
bar4.setText(getKey2);
} else if (actualshippersnum == optimum20) {
getKey3 = sharedPreferences.getInt("Key3", percentageActual20);
bar4.setText(getKey3);
}
else if (spinnerSelection.equals("S1") && spinnerSelection2.equals("30")) {
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(Dashboard.this);
builder.setTitle("Refresh Error");
builder.setMessage("No SP found");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (actualshippersnum > optimum30) {
getKey4 = sharedPreferences.getInt("Key4", plus30);
bar4.setText(getKey4);
} else if (actualshippersnum < optimum30) {
getKey5 = sharedPreferences.getInt("Key5", minus30);
bar4.setText(getKey5);
} else if (actualshippersnum == optimum30) {
getKey6 = sharedPreferences.getInt("Key6", percentageActual30);
bar4.setText(getKey6);
}
}
if (spinnerSelection == null || spinnerSelection2 == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(Dashboard.this);
builder.setTitle("Data Input Error");
builder.setMessage("No SP found");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (spinnerSelection.equals("S2") && spinnerSelection2.equals("20")) {
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(Dashboard.this);
builder.setTitle("Refresh Error");
builder.setMessage("No SP found");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (actualshippersnum > optimum20) {
getKey7 = sharedPreferences.getInt("Key7", plus20);
bar5.setText(getKey7);
} else if (actualshippersnum < optimum20) {
getKey8 = sharedPreferences.getInt("Key8", minus20);
bar4.setText(getKey8);
} else if (actualshippersnum == optimum20) {
getKey9 = sharedPreferences.getInt("Key9", percentageActual20);
bar4.setText(getKey9);
}
} else if (spinnerSelection.equals("S2") && spinnerSelection2.equals("30")) {
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(Dashboard.this);
builder.setTitle("Refresh Error");
builder.setMessage("No SP found");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (actualshippersnum > optimum30) {
getKey10 = sharedPreferences.getInt("Key10", plus30);
bar4.setText(getKey10);
} else if (actualshippersnum < optimum30) {
getKey11 = sharedPreferences.getInt("Key11", minus30);
bar4.setText(getKey11);
} else if (actualshippersnum == optimum30) {
getKey12 = sharedPreferences.getInt("Key12", percentageActual30);
bar4.setText(getKey12);
}
}
if (spinnerSelection == null || spinnerSelection2 == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(Dashboard.this);
builder.setTitle("Data Input Error");
builder.setMessage("Line S3 Data has not been entered yet!");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (spinnerSelection.equals("S3")) {
if (spinnerSelection2.equals("20")) {
//HAVENT FILLED INTO DECOVIEW - 20
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(Dashboard.this);
builder.setTitle("Refresh Error");
builder.setMessage("Cannot Refresh! Please Fill in Line Details");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (actualshippersnum > optimum20) {
getKey13 = sharedPreferences.getInt("Key13", plus20);
bar6.setText(getKey13);
} else if (actualshippersnum < optimum20) {
getKey14 = sharedPreferences.getInt("Key14", minus20);
bar6.setText(getKey14);
} else if (actualshippersnum == optimum20) {
getKey15 = sharedPreferences.getInt("Key15", percentageActual20);
bar6.setText(getKey15);
}
} else if (spinnerSelection2.equals("30")) {
//HAVENT FILLED INTO DECOVIEW - 30
if (actualshippersnum == null) {
AlertDialog.Builder builder = new AlertDialog.Builder(Dashboard.this);
builder.setTitle("Refresh Error");
builder.setMessage("Cannot Refresh! Please Fill in Line Details");
builder.setIcon(R.drawable.warning_icon);
builder.setCancelable(true);
builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
dialog.cancel();
}
});
AlertDialog alert = builder.create();
alert.show();
} else if (actualshippersnum > optimum30) {
getKey16 = sharedPreferences.getInt("Key16", plus30);
bar6.setText(getKey16);
} else if (actualshippersnum < optimum30) {
getKey17 = sharedPreferences.getInt("Key17", minus30);
bar6.setText(getKey17);
} else if (actualshippersnum == optimum30) {
getKey18 = sharedPreferences.getInt("Key18", percentageActual30);
bar6.setText(getKey18);
【问题讨论】：
-
如果您发布一些代码会更容易提供帮助。
-
应该可以，但是你应该检查你的共享偏好键是否有一个值，通过检查它是否为空，否则如果它是一个字符串。在将其设置为 textview 之前，从 onCreate 和 onResume 中获取值（以防第二个活动的 onbackpressed）
-
我已经添加了代码:)
-
@MaciejBiałorucki
-
我认为您应该在 Line Details 活动中对编辑器对象调用 apply() 或 commit()。
标签： java android nullpointerexception sharedpreferences