Android 运行 仅在第一个 运行 上设置 activity
Android run setup activity on first run only
我正在开发我的第一个 android 应用程序,我的主 activity 上有一个微调器,当用户在登陆屏幕或 activity 之后运行该应用程序时一个不同的基于(不是主要的)。我将微调器的选择存储在共享偏好中,如果已设置,我想在启动时加载不同的 activity。
代码
private Spinner spinner;
private SharedPreferences favTeam;
//private SharedPreferences.Editor editor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/*
if (favTeam.contains("team") && favTeam != null) {
Intent intent = new Intent(this, MyTeamActivity.class);
startActivity(intent);
} else {
System.out.println("-------- cant read from shared pref -----------");
}
*/
spinner = (Spinner) findViewById(R.id.selectTeam);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.teams_array, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
}
public void submitMyTeam(View v){
favTeam = this.getSharedPreferences("com.lonerganonline.league_of_ireland", Context.MODE_PRIVATE);
//SharedPreferences favTeam = this.getSharedPreferences("com.lonerganonline.league_of_ireland", Context.MODE_PRIVATE);
TextView txt = (TextView) findViewById(R.id.textView);
String selectedTeam = spinner.getSelectedItem().toString();
SharedPreferences.Editor editor = favTeam.edit();
editor.putString("team", selectedTeam);
editor.apply();
Intent intent = new Intent(this, MyTeamActivity.class);
txt.setText(favTeam.getString("team","Not Defined"));
startActivity(intent);
}
我尝试通过上面代码中注释掉的 if 语句来执行此操作,但这导致了致命错误。
任何帮助将不胜感激。
因为您试图从 favTeam
中读取值而不对其进行初始化。这就是为什么它不起作用并且您得到 NullPointerException.
您必须先初始化 favteam ShardePreference
,然后才能从中读取值,
使用
favTeam = this.getSharedPreferences("com.lonerganonline.league_of_ireland", Context.MODE_PRIVATE);
在 onCreate()
所以你的代码看起来像,
favTeam = this.getSharedPreferences("com.lonerganonline.league_of_ireland", Context.MODE_PRIVATE);
if (favTeam.contains("team") && favTeam != null) {
Intent intent = new Intent(this, MyTeamActivity.class);
startActivity(intent);
} else {
System.out.println("-------- cant read from shared pref -----------");
}
如果您仍然遇到错误,那么 post 错误日志。
我正在开发我的第一个 android 应用程序,我的主 activity 上有一个微调器,当用户在登陆屏幕或 activity 之后运行该应用程序时一个不同的基于(不是主要的)。我将微调器的选择存储在共享偏好中,如果已设置,我想在启动时加载不同的 activity。
代码
private Spinner spinner;
private SharedPreferences favTeam;
//private SharedPreferences.Editor editor;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
/*
if (favTeam.contains("team") && favTeam != null) {
Intent intent = new Intent(this, MyTeamActivity.class);
startActivity(intent);
} else {
System.out.println("-------- cant read from shared pref -----------");
}
*/
spinner = (Spinner) findViewById(R.id.selectTeam);
ArrayAdapter<CharSequence> adapter = ArrayAdapter.createFromResource(this, R.array.teams_array, android.R.layout.simple_spinner_item);
adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
spinner.setAdapter(adapter);
}
public void submitMyTeam(View v){
favTeam = this.getSharedPreferences("com.lonerganonline.league_of_ireland", Context.MODE_PRIVATE);
//SharedPreferences favTeam = this.getSharedPreferences("com.lonerganonline.league_of_ireland", Context.MODE_PRIVATE);
TextView txt = (TextView) findViewById(R.id.textView);
String selectedTeam = spinner.getSelectedItem().toString();
SharedPreferences.Editor editor = favTeam.edit();
editor.putString("team", selectedTeam);
editor.apply();
Intent intent = new Intent(this, MyTeamActivity.class);
txt.setText(favTeam.getString("team","Not Defined"));
startActivity(intent);
}
我尝试通过上面代码中注释掉的 if 语句来执行此操作,但这导致了致命错误。 任何帮助将不胜感激。
因为您试图从 favTeam
中读取值而不对其进行初始化。这就是为什么它不起作用并且您得到 NullPointerException.
您必须先初始化 favteam ShardePreference
,然后才能从中读取值,
使用
favTeam = this.getSharedPreferences("com.lonerganonline.league_of_ireland", Context.MODE_PRIVATE);
在 onCreate()
所以你的代码看起来像,
favTeam = this.getSharedPreferences("com.lonerganonline.league_of_ireland", Context.MODE_PRIVATE);
if (favTeam.contains("team") && favTeam != null) {
Intent intent = new Intent(this, MyTeamActivity.class);
startActivity(intent);
} else {
System.out.println("-------- cant read from shared pref -----------");
}
如果您仍然遇到错误,那么 post 错误日志。