android savedinstancestate null啥原因

Posted 2023-04-26

参考技术A package cn.teachcourse.main;import cn.teachcourse.bean.WeatherBean;import android.content.Intent;import android.os.Bundle;import android.support.v7.app.ActionBarActivity;import android.view.Menu;import android.view.MenuItem;import android.widget.TextView;public class MainActivity extends ActionBarActivity private TextView mTextView; private WeatherBean mBean; @Override protected void onCreate(Bundle savedInstanceState) super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initView(); private void initView() mTextView = (TextView) findViewById(R.id.textview1); @Override public boolean onCreateOptionsMenu(Menu menu) // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; @Override public boolean onOptionsItemSelected(MenuItem item) // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); if (id == R.id.action_settings) return true; return super.onOptionsItemSelected(item); @Override protected void onSaveInstanceState(Bundle outState) super.onSaveInstanceState(outState); // 保存天气状态 outState.putSerializable("WeatherBean", new WeatherBean("2016-01-19", "广州")); @Override protected void onRestoreInstanceState(Bundle savedInstanceState) super.onRestoreInstanceState(savedInstanceState); // 获取保存的状态 mBean = (WeatherBean) savedInstanceState.getSerializable("WeatherBean"); if (savedInstanceState != null) mTextView.setText(mBean.getCity() + ";" + mBean.getDate());

android如何获取控件宽度

如下列代码，经测试，Toast显示width2确实为控件TextView的宽度，但显示的width1仍然为初始值0，如何将width2的值赋给全局变量width1呢？求大神们指教！

public class MainActivity extends Activity
private TextView txt = null;
private int width1 = 0;

protected void onCreate(Bundle savedInstanceState)
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

txt = (TextView) findViewById(R.id.txt);
ViewTreeObserver vto = txt.getViewTreeObserver();

vto.addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener()
public boolean onPreDraw()
int width2 = txt.getMeasuredWidth();
Toast.makeText(getApplication(), "width2:" + width2, Toast.LENGTH_SHORT).show();
width1 = width2;
return true;

);

Toast.makeText(getApplication(), "width1:" + width1, Toast.LENGTH_SHORT).show();

参考技术A 用getWidth()方法，可以获取像素单位的宽度。

android的控件一般是继承的android.View这个类，所以可以直接用View#getWidth()方法获取控件宽度。另外这个方法是final方法，无法被子类覆盖，所以可以安心调用 参考技术B 是不是第二个Toast比第一个先输出？ 如果是，问题就在于监听器的回调方法执行时间比第二个Toast晚。追问

我是想在程序一开始运行的时候就能获取width2的值并用于其它计算，请问该如何获取width2的值？

追答

把你的逻辑代码写在onPreDraw回调方法里

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