这种情况是正常的
private Button button;
private Button button1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button = (Button)findViewById(R.id.button);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SharedPreferences.Editor editor = getSharedPreferences("data", 0).edit();
editor.putInt("yi", 1);
editor.putString("er", "二");
editor.apply();
Toast.makeText(MainActivity.this, "complete", Toast.LENGTH_SHORT).show();
}
});
这样就会报空指针错
private Button button= (Button)findViewById(R.id.button);;
private Button button1;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
SharedPreferences.Editor editor = getSharedPreferences("data", 0).edit();
editor.putInt("yi", 1);
editor.putString("er", "二");
editor.apply();
Toast.makeText(MainActivity.this, "complete", Toast.LENGTH_SHORT).show();
}
});
请问这两种的区别在哪里?