我在Android应用程序中遇到问题,其中SharedPreferences崩溃了应用程序。我正在创建一个货币转换器应用程序,所以我创建了一个SharedPreferences,以便在没有互联网连接时保存该值。我已经在谷歌搜索了一个星期,但我找不到答案。这是我的代码:
if (text1.equals("US Dollar - USD") && text2.equals("Euro - EUR")
&& edittextdollars.length() > 0
&& edittexteuros.length() == 0) {
Thread thread = new Thread(new Runnable() {
@Override
public void run() {
try {
handler.sendEmptyMessage(2);
String hello = edittextdollars.getText().toString();
double hello3 = Double.parseDouble(hello);
//getGraph("USD", "EUR");
convertvalues("USD", "EUR");
String hello2 = edittexteuros.getText().toString();
double hello4 = Double.parseDouble(hello2);
textview2.setText(String.valueOf(hello4 / hello3));
SharedPreferences settings = getSharedPreferences("1", 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString("eurusd", textview2.getText().toString());
editor.commit();
} catch (Exception e) {
}
}
});
thread.start();
}
@SuppressLint("HandlerLeak")
public Handler handler = new Handler() {
public void handleMessage(android.os.Message msg) {
dialog1.dismiss();
try {
switch (msg.what) {
case 2:
try {
String hello = edittextdollars.getText().toString();
double hello3 = Double.parseDouble(hello);
//getGraph("USD", "EUR");
convertvalues("USD", "EUR");
String hello2 = edittexteuros.getText().toString();
double hello4 = Double.parseDouble(hello2);
textview2.setText(String.valueOf(hello4 / hello3));
} catch (Exception e) {
SharedPreferences settings = getSharedPreferences("1", 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString("eurusd", j);
editor.commit();
//textview2.setVisibility(View.INVISIBLE);
}
break;
我唯一困惑的是SharedPreferences部分。
请忽略 handler.sendEmptyMessage(2);
String hello = edittextdollars.getText().toString();
double hello3 = Double.parseDouble(hello);
//getGraph("USD", "EUR");
convertvalues("USD", "EUR");
String hello2 = edittexteuros.getText().toString();
double hello4 = Double.parseDouble(hello2);
textview2.setText(String.valueOf(hello4 / hello3));
这很好。现在,当我添加这个......
SharedPreferences settings = getSharedPreferences("1", 0);
SharedPreferences.Editor editor = settings.edit();
editor.putString("eurusd", j);
editor.commit();
这就是我撞墙的地方。这有什么不对?为了以防万一,我将发布LogCat。
09-04 22:06:57.088: E/AndroidRuntime(887): FATAL EXCEPTION: main
09-04 22:06:57.088: E/AndroidRuntime(887): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.example.currencyconverter/com.example.currencyconverter.MainActivity2}: java.lang.NullPointerException
09-04 22:06:57.088: E/AndroidRuntime(887): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2106)
09-04 22:06:57.088: E/AndroidRuntime(887): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
09-04 22:06:57.088: E/AndroidRuntime(887): at android.app.ActivityThread.access$600(ActivityThread.java:141)
09-04 22:06:57.088: E/AndroidRuntime(887): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
09-04 22:06:57.088: E/AndroidRuntime(887): at android.os.Handler.dispatchMessage(Handler.java:99)
09-04 22:06:57.088: E/AndroidRuntime(887): at android.os.Looper.loop(Looper.java:137)
09-04 22:06:57.088: E/AndroidRuntime(887): at android.app.ActivityThread.main(ActivityThread.java:5041)
09-04 22:06:57.088: E/AndroidRuntime(887): at java.lang.reflect.Method.invokeNative(Native Method)
09-04 22:06:57.088: E/AndroidRuntime(887): at java.lang.reflect.Method.invoke(Method.java:511)
09-04 22:06:57.088: E/AndroidRuntime(887): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
09-04 22:06:57.088: E/AndroidRuntime(887): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
09-04 22:06:57.088: E/AndroidRuntime(887): at dalvik.system.NativeStart.main(Native Method)
09-04 22:06:57.088: E/AndroidRuntime(887): Caused by: java.lang.NullPointerException
09-04 22:06:57.088: E/AndroidRuntime(887): at com.example.currencyconverter.MainActivity2.<init>(MainActivity2.java:102)
09-04 22:06:57.088: E/AndroidRuntime(887): at java.lang.Class.newInstanceImpl(Native Method)
09-04 22:06:57.088: E/AndroidRuntime(887): at java.lang.Class.newInstance(Class.java:1319)
09-04 22:06:57.088: E/AndroidRuntime(887): at android.app.Instrumentation.newActivity(Instrumentation.java:1054)
09-04 22:06:57.088: E/AndroidRuntime(887): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2097)
09-04 22:06:57.088: E/AndroidRuntime(887): ... 11 more
提前感谢您考虑我的问题。
答案 0 :(得分:0)
你需要这样做:
SharedPreferences settings = mContext.getSharedPreferences("1", 0);