我做的应用程序,显示你的随机数选择最小和最大次数后。但是旋转的结果后消失了,所以我的onSaveInstanceState实施和定制的为我的需要,在那之后我的应用程序崩溃,所有的时间。
公共类MainActivity扩展AppCompatActivity {
EditText et_min,et_max;
Button button;
TextView tv_output;
Random r;
int min, max, output;
private static final String STATE_TV_OUTPUT = "tv_output";
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
String onSave = savedInstanceState.getString("onSave");
}
@Override
protected void onSaveInstanceState(Bundle SavedInstanceState) {
super.onSaveInstanceState(SavedInstanceState);
SavedInstanceState.putString("onSave", "1");
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
r = new Random();
String onSave = tv_output.getText().toString();
et_max = (EditText) findViewById(R.id.et_max);
et_min = (EditText) findViewById(R.id.et_min);
button = (Button) findViewById(R.id.button);
tv_output = (TextView) findViewById(R.id.tv_output);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String tempMin, tempMax;
tempMin = et_min.getText().toString();
tempMax = et_max.getText().toString();
if (!tempMin.equals("") && !tempMax.equals(""))//ovde stavljam ih u poziciju gde su slobodni za pisanje
min = Integer.parseInt(tempMin);
max = Integer.parseInt(tempMax);//ova dva sluze kako bi pretvorili stringove u intove za potrebe dole methoda
if (max > min) {
output = r.nextInt((max - min) + 1) + min;//nextInt sluzi kako bi dao random broj izmedju dva broja u ovom slucaju min i max
tv_output.setText("" + output);
}
}
});
}
}
您需要更改顺序,否则改变束不会通过:
@Override
protected void onSaveInstanceState(Bundle savedInstanceState) {
savedInstanceState.putString("onSave", "1");
super.onSaveInstanceState(savedInstanceState);
}
在调用super
类的方法并不总是最上面的一个。
什么是logcat的输出?
您可以在此处详细了解Android的活动周期:https://developer.android.com/guide/components/activities/activity-lifecycle#java
您的代码保存和恢复状态将是这样的:
static final String STATE_KEY = "onSave";
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
String onSave = savedInstanceState.getString(STATE_KEY);
}
@Override
protected void onSaveInstanceState(Bundle SavedInstanceState) {
SavedInstanceState.putString(STATE_KEY, "1");
super.onSaveInstanceState(SavedInstanceState);//call this at the end
}
把这一行
String onSave = tv_output.getText().toString();
tv_output
初始化后,否则你将得到NullPointerException异常。
更新:
要保存的TextView文本旋转过程中,添加android:freezesText="true"
到XML(What is (s/g)etFreezesText in TextView?),没有必要使用的onSaveInstanceState。