settings.java
public class settingsActivity extends MainActivity {
private TextView mTextMessage;
Intent i=new Intent();
Button saveButton;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
goalDate = findViewById(R.id.goaldinput);
goalWeight = findViewById(R.id.goalwinput);
nameIn = findViewById(R.id.nameinput);
fT=findViewById(R.id.feet);
iNches=findViewById(R.id.inches);
mAle=findViewById(R.id.maleButton);
feMale=findViewById(R.id.othersButton);
oThers=findViewById(R.id.femaleButton);
switch (item.getItemId()) {
case R.id.navigation_home:
mTextMessage.setText(R.string.title_home);
Intent intent1 = new Intent(settingsActivity.this, MainActivity.class);
startActivity(intent1);
break;
case R.id.navigation_history:
mTextMessage.setText(R.string.title_history);
Intent intent2 = new Intent(settingsActivity.this, historyActivity.class);
startActivity(intent2);
break;
case R.id.navigation_progress:
mTextMessage.setText(R.string.title_progress);
Intent intent3 = new Intent(settingsActivity.this, progressActivity.class);
startActivity(intent3);
break;
case R.id.navigation_settings:
mTextMessage.setText(R.string.title_settings);
Intent intent4 = new Intent(settingsActivity.this, settingsActivity.class);
startActivity(intent4);
break;
}
return false;
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_settings);
mTextMessage = (TextView) findViewById(R.id.message);
BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
saveButton=findViewById(R.id.saveButton);
saveButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
EditText goalD = ((EditText)findViewById(R.id.goaldinput));
EditText goalW = ((EditText)findViewById(R.id.goalwinput));
EditText currentW = ((EditText)findViewById(R.id.currentWinput));
i = new Intent(settingsActivity.this,historyActivity.class);
gD=goalD.getText().toString();
gW=goalW.getText().toString();
cW=currentW.getText().toString();
i.putExtra("goalDate",gD);
i.putExtra("goalWeight",gW);
i.putExtra("currentWeight",cW);
startActivity(i);
/*
arrayList1.add(goalD.toString());
arrayList2.add(goalW.toString());
arrayList3.add(currentW.toString());
*/
// adapter1.notifyDataSetChanged();
// adapter2.notifyDataSetChanged();
// adapter3.notifyDataSetChanged();
}
});
}
history.java
public class historyActivity extends MainActivity {
private TextView mTextMessage;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.navigation_home:
mTextMessage.setText(R.string.title_home);
Intent intent1 = new Intent(historyActivity.this, MainActivity.class);
startActivity(intent1);
break;
case R.id.navigation_history:
mTextMessage.setText(R.string.title_history);
Intent intent2 = new Intent(historyActivity.this, historyActivity.class);
startActivity(intent2);
break;
case R.id.navigation_progress:
mTextMessage.setText(R.string.title_progress);
Intent intent3 = new Intent(historyActivity.this, progressActivity.class);
startActivity(intent3);
break;
case R.id.navigation_settings:
mTextMessage.setText(R.string.title_settings);
Intent intent4 = new Intent(historyActivity.this, settingsActivity.class);
startActivity(intent4);
break;
}
return false;
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
mTextMessage = (TextView) findViewById(R.id.message);
BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
listView1= findViewById(R.id.goaldlistView);
listView2= findViewById(R.id.goalwlistView);
listView3= findViewById(R.id.currentwlistView);
EditText goalD = ((EditText)findViewById(R.id.goaldinput));
EditText goalW = ((EditText)findViewById(R.id.goalwinput));
EditText currentW = ((EditText)findViewById(R.id.currentWinput));
gDate = getIntent().getExtras().getString("goalDate");
gWeight = getIntent().getExtras().getString("goalWeight");
cWeight = getIntent().getExtras().getString("currentWeight");
String addArray1[] = {"3/14/1992"};
String addArray2[] = {"152"};
String addArray3[] = {"160"};
arrayList1=new ArrayList<String>(Arrays.asList(addArray1));
arrayList2=new ArrayList<String>(Arrays.asList(addArray2));
arrayList3=new ArrayList<String>(Arrays.asList(addArray3));
arrayList1.add(gDate);
arrayList2.add(gWeight);
arrayList3.add(cWeight);
adapter1 = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,arrayList1);
adapter2 = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,arrayList2);
adapter3 = new ArrayAdapter<String>(this,android.R.layout.simple_list_item_1,arrayList3);
listView1.setAdapter(adapter1);
listView2.setAdapter(adapter2);
listView3.setAdapter(adapter3);
}
}
MainActivity.java
public class MainActivity extends AppCompatActivity {
private TextView mTextMessage;
EditText goalDate ;
EditText goalWeight ;
EditText nameIn ;
EditText fT;
EditText iNches;
EditText currentWeight;
RadioButton mAle;
RadioButton feMale;
RadioButton oThers;
public ArrayList<String>arrayList1=new ArrayList<String>();
public ArrayList<String>arrayList2=new ArrayList<String>();
public ArrayList<String>arrayList3=new ArrayList<String>();
public ArrayAdapter<String> adapter1;
public ArrayAdapter<String> adapter2;
public ArrayAdapter<String> adapter3;
Intent intent =new Intent();
public ListView listView1;
public ListView listView2;
public ListView listView3;
String gD=" ";
String gW=" ";
String cW=" ";
String gDate=" ";
String gWeight=" ";
String cWeight=" ";
;
private BottomNavigationView.OnNavigationItemSelectedListener mOnNavigationItemSelectedListener
= new BottomNavigationView.OnNavigationItemSelectedListener() {
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.navigation_home:
mTextMessage.setText(R.string.title_home);
Intent intent1 = new Intent(MainActivity.this, MainActivity.class);
startActivity(intent1);
break;
case R.id.navigation_history:
mTextMessage.setText(R.string.title_history);
Intent intent2 = new Intent(MainActivity.this, historyActivity.class);
startActivity(intent2);
break;
case R.id.navigation_progress:
mTextMessage.setText(R.string.title_progress);
Intent intent3 = new Intent(MainActivity.this, progressActivity.class);
startActivity(intent3);
break;
case R.id.navigation_settings:
mTextMessage.setText(R.string.title_settings);
Intent intent4 = new Intent(MainActivity.this, settingsActivity.class);
startActivity(intent4);
break;
}
return false;
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextMessage = (TextView) findViewById(R.id.message);
BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}
将数据从设置传递到历史记录时出现以下错误：
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.os.Bundle.getString(java.lang.String)' on a null object reference
gDate是错误的bundle的nullException错误，我认为它可能适用于gWeight和cWeight
我尝试初始化MainActivity，Setting和History文件中的意图。仍然没有传递数据。
需要传递“设置”中的输入并显示在“历史记录”中的listView中
答案 0 :(得分：0)
您不需要写
Intent intent = new Intent();在您的“历史记录”课程中。
代替这篇文章。
Intent intent = getIntent();
gDate = intent.getExtras().getString("goalDate");
gWeight = intent.getExtras().getString("goalWeight");
cWeight = intent.getExtras().getString("currentWeight");
-更新-
删除意图i = new Intent（）;来自“设置”活动的父级。
在onCreate（）中做到这一点。
saveButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent i = new Intent(settingsActivity.this,historyActivity.class);
String gD = goalD.getText().toString();
String gW = goalW.getText().toString();
String cW = currentW.getText().toString();
i.putExtra("goalDate",gD);
i.putExtra("goalWeight",gW);
i.putExtra("currentWeight",cW);
startActivity(i);
}
});
在“历史记录”活动中：
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_history);
Intent intent = getIntent();
String gDate = intent.getExtras().getString("goalDate");
String gWeight = intent.getExtras().getString("goalWeight");
String cWeight = intent.getExtras().getString("currentWeight");
// OR
Intent intent = getIntent();
String gDate = intent.getStringExtra("goalDate");
String gWeight = intent.getStringExtra("goalWeight");
String cWeight = intent.getStringExtra("currentWeight");
}
我也建议您添加支票。
if(intent.getExtras() != null) {
//Your code here.
}
-更新2 ---
您在评论中说：“但是当我按下导航工具栏中的历史记录按钮时，该程序将在nullPointerException上退出”。这是正常现象，因为单击导航工具栏中的“历史记录”按钮后，此代码才可以在设置片段中使用。
case R.id.navigation_history:
mTextMessage.setText(R.string.title_history);
Intent intent2 = new Intent(settingsActivity.this, historyActivity.class);
startActivity(intent2);
break;
您看到这里没有调用任何putExtra（），因此当它打开历史记录时，它将通过nullPointerException，因为您在历史记录类中调用了getExtra（），但是由于您没有添加任何额外的内容，因此getExtra（）将返回null。因此，防止这种情况的唯一方法是在这种情况下添加putExtra（）或在获得额外附加值之前进行检查。
Intent intent = getIntent();
if(intent.getExtras() != null) { //Also there is hasExtra() check too, but I'd like to check like this.
gDate = intent.getExtras().getString("goalDate");
gWeight = intent.getExtras().getString("goalWeight");
cWeight = intent.getExtras().getString("currentWeight");
}